Aplastic anemia: clinical guidelines

List of Abbreviations

AA — aplastic anemia

allo-HSCT – allogeneic hematopoietic stem cell transplantation

ATG – antithymocyte globulin**

ALT – alanine aminotransferase

AST - aspartate aminotransferase

aPTT – activated partial thromboplastin time

ULN – upper limit of normal

HAA – hepatitis-associated aplastic anemia

G-CSF – colony-stimulating factors (L03AA according to the ATC classification)

GPI – glycosylphosphatidylinositol

IL – interleukin

IST – immunosuppressive therapy

IFNγ – interferon gamma**

CT – clinical trials

BM – bone marrow

CT – computed tomography

LDH – lactate dehydrogenase

MDS — myelodysplastic syndrome

MonAb – monoclonal antibodies

NAA – non-severe aplastic anemia

PNH — paroxysmal nocturnal hemoglobinuria

AML – acute myeloid leukemia

CR – complete remission

PT – prothrombin index

VSAA – very severe aplastic anemia

HSC — hematopoietic stem cell

SAA – severe aplastic anemia

HSCT – hematopoietic stem cell transplantation

LCE – level of confidence of evidence

US – ultrasound examination

GRS – grade of recommendation strength

TNFα – tumor necrosis factor alpha

Cs – #ciclosporin**

PR – partial remission

ECG – electrocardiography

EchoCG – echocardiography

CD – clusters of differentiation

HLA – human leukocyte antigens

PIG-A – phosphatidylinositol glycan class A

Th – T-helper cells

Treg – T-regulatory cells

NK – natural killer cells

FISH – fluorescence in situ hybridization

Terms and Definitions

Aplastic anemia (AA) is a hematologic disorder characterized by pancytopenia resulting from bone marrow aplasia, associated with impaired immune mechanisms of hematopoiesis regulation, quantitative deficiency, and functional defects of hematopoietic stem cells

Combined immunosuppressive therapy (IST) in patients with AA is performed according to a protocol including antithymocyte globulin of animal origin for human use (ATG)** and ciclosporin (Cs)**.

Programmed treatment of patients with AA is a set of therapeutic measures performed step-by-step from the moment of disease diagnosis, implemented according to a specific algorithm, including ATG**, Cs**, and, if necessary, repeated courses of ATG and other treatment methods that allow achieving long-term patient survival.

Paroxysmal nocturnal hemoglobinuria clone (PNH clone) is a hematopoietic stem cell (HSC) clone with a mutation in the PIG-A gene, leading to impaired synthesis of glycosylphosphatidylinositol (GPI).

Complete remission is complete normalization of hemogram parameters

Partial remission is partial normalization of hemogram parameters (hemoglobin 90–100.0 g/L, granulocytes >1.0–1.5 × 10⁹/L, platelets >100 × 10⁹/L) and no need for blood component replacement therapy.

Clinico-hematological improvement (minimal hematological response) is improvement in hemogram parameters (hemoglobin 70.0–85 g/L, granulocytes >0.5–1.0 × 10⁹/L, platelets >20.0 × 10⁹/L), disappearance or significant reduction of dependence on blood component transfusions.

Refractory AA is diagnosed in the absence of a response to ongoing combined IST at 6–9 months from the start of IST treatment or after the second stage of treatment (after the second course of ATG**).

1. Brief information on the disease or condition

1.1 Definition of the disease or condition

Aplastic anemia is a hematologic disorder characterized by pancytopenia resulting from bone marrow aplasia, associated with impaired immune mechanisms of hematopoiesis regulation, quantitative deficiency, and functional defects of HSCs.

1.2 Etiology and pathogenesis of the disease or condition (group of diseases or conditions)

One of the leading mechanisms of hematopoietic impairment in AA is considered to be immune aggression directed against hematopoietic progenitor cells [1].

Bone marrow failure in AA develops as a result of the suppression of hematopoietic progenitor cell proliferation by activated T lymphocytes and natural killer cells. Activation of T lymphocytes, expansion of cytotoxic T clones, and release of mediators of immune suppression of hematopoiesis (interferon gamma [IFNγ], tumor necrosis factor alpha) or those stimulating T-lymphocyte proliferation and activation (interleukin-2) lead to impaired proliferation and stimulation of progenitor cell apoptosis, resulting in a significant reduction in the hematopoietic cell pool and the development of bone marrow aplasia [1–3].

Reduction of the bone marrow hematopoietic cell pool is accompanied by impaired iron metabolism and deposition of toxic iron in both the bone marrow and the myocardium and liver, which causes dysfunction of these organs [1].

The main clinical manifestations of the disease are anemia syndrome, hemorrhagic syndrome, and severe infectious complications [2]. In addition, the course of AA can be complicated by the development of clonal diseases such as paroxysmal nocturnal hemoglobinuria (PNH), myelodysplastic syndrome (MDS), and acute myeloid leukemia (AML). The incidence of clonal complications can reach 32% within 10 years [3, 4]. The appearance of clonal hematopoiesis can be detected at earlier stages of the course of AA as well. This primarily refers to AA occurring with a PNH clone [5, 6]. At the same time, the detection of a clone with a deficiency of glycosylphosphatidylinositol (GPI) proteins does not mean the development of PNH as an independent disease with the picture of classical intravascular hemolysis. The size of the PNH clone during the course of AA can change until complete disappearance [7]. Evolution into classical PNH, according to various authors, is 11–17% [8–10].

1.3 Epidemiology of the Disease or Condition

According to epidemiological studies, aplastic anemia occurs with varying frequencies in regions such as Europe, North America, and the Far and Middle East; meanwhile, according to the International Agranulocytosis and Aplastic Anemia Study, the prevalence of AA in European countries is 2 cases per 1 million population per year, with this indicator fluctuating depending on the specific country from 0.6 to 3 or more cases per 1 million population per year [11].

1.4 Features of Coding the Disease or Condition

Other aplastic anemias (D61)

D61.1 – Drug-induced aplastic anemia

D61.3 – Idiopathic aplastic anemia

D61.8 – Other specified aplastic anemias

D61.9 – Aplastic anemia, unspecified

1.5 Classification of the disease or condition

Acquired AA:

1. Idiopathic AA

2. Secondary AA

• Radiation

• Drugs and chemical toxins

• Viruses

• Immunopathology

• Pregnancy

The following criteria for the severity of acquired AA are distinguished:

• non-severe AA: granulocytopenia >0.5 × 10⁹/L;

• severe AA: granulocytopenia <0.5 × 10⁹/L, thrombocytopenia <20.0 × 10⁹/L);

• very severe (extremely severe) AA: granulocytopenia <0.2 × 10⁹/L.

When determining the severity of AA, the results of at least three peripheral blood tests at the time of disease diagnosis before the start of treatment are taken into account [12, 13].

It is also customary to distinguish three clinical variants of AA depending on the detection of a PNH clone:

• AA occurring without a PNH clone

• AA occurring with a PNH clone

• AA occurring with PNH syndrome (subclinical or clinical signs of intravascular hemolysis)

1.6 Clinical presentation of the disease or condition

The manifestation of clinical manifestations of AA is accompanied by complaints of an anemia nature, the development of hemorrhagic syndrome of varying intensity, and infectious complications against the background of profound tri-lineage cytopenia. These manifestations can develop acutely or increase gradually, depending on the severity of AA.

The clinical picture of AA, especially in severe and very severe forms of the disease, can be influenced by clinical symptoms of complications, including life-threatening ones, which often develop in patients with AA both before and during treatment. The most common complications include bacterial, viral, and fungal infections, including septic shock, renal failure, hemorrhagic complications including intracranial hemorrhages and menorrhagia, neurological and psychiatric disorders; peptic ulcer disease and/or aseptic osteonecrosis may develop during glucocorticosteroid therapy.

2. Diagnostics, medical indications and contraindications for diagnostic methods

Many recommended methods for diagnosing the disease and related conditions have a limited evidence base in accordance with the grading scales for the levels of evidence certainty (LEC) and levels of clinical recommendation consensus (LCRC) due to the lack of clinical studies devoted to them. Despite this, they are necessary elements of patient examination to establish a diagnosis and choose treatment tactics, since more effective and proven methods have not been developed at present.

The diagnosis of AA is established based on clinical manifestations and laboratory examination data.

• Tri-lineage cytopenia: anemia (hemoglobin <110 g/L), granulocytopenia (granulocytes <2.0 × 10⁹/L), thrombocytopenia (platelets <100.0 × 10⁹/L).

• Decreased bone marrow (BM) cellularity and absence of megakaryocytes according to BM aspiration data.

• BM aplasia in an iliac crest biopsy (predominance of fatty BM).

The following criteria for AA severity are distinguished:

• non-severe AA: granulocytopenia >0.5 × 10⁹/L;

• severe AA: granulocytopenia <0.5 × 10⁹/L, thrombocytopenia <20.0 × 10⁹/L);

• very severe (extremely severe) AA: granulocytopenia <0.2 × 10⁹/L).

When determining the severity of AA, the results of at least three peripheral blood tests at the time of disease diagnosis prior to the initiation of treatment are taken into account [14, 15].

2.1 Complaints and Anamnesis

Comments: the history of the disease should describe all episodes of infectious complications, administered antibacterial therapy, and bacteriological culture data. A full description of the frequency of and need for ongoing transfusion therapy is required, along with data collection on post-transfusion complications.

2.2 Physical Examination

Comments: during the physical examination, it is necessary to differentiate anomalies characteristic of constitutional forms of AA (stature, facial features, skin pigmentation, nail dystrophy, mucosal leukoplakia, eye development anomalies, dental anomalies, premature graying and hair loss, hypogonadism, etc.).

2.3 Laboratory Diagnostics

Comments: to determine the severity of AA, 3 consecutive blood tests are required. During treatment monitoring, the complete (clinical) blood count is performed twice a week until a response is achieved, and thereafter once a month [12].

Comments: to study hemostatic parameters, blood collection must be performed strictly on an empty stomach using vacuum collection tubes. Blood collection from catheters is prohibited. Blood is collected into tubes containing 3.2% sodium citrate at a 1:9 ratio. The test must be performed no later than 2 hours after blood collection. The reliability of platelet aggregation results can only be assessed when the blood platelet count is ≥ 100×10⁹/L.

Comments: frequent donor red blood cell transfusions may lead to secondary hemosiderosis of organs and tissues.

Comments: in AA, the bone marrow aspirate is hypocellular, relative lymphocytosis is determined, and megakaryocytes are absent. Sternal puncture can be performed in patients with severe thrombocytopenia without prior transfusion preparation [23].

Comments: the detection of clonal aberrations characteristic of MDS rules out the diagnosis of acquired AA. FISH testing using probes most characteristic of MDS/AML (to determine chromosome 7 anomalies, trisomy 8, 5q deletion) is necessary despite the absence of cytogenetic aberrations or mitoses in standard cytogenetic testing.

Comments: bilateral trephine biopsy of the anterior or posterior iliac spines must be performed

Comments: determination of the number of sideroblasts and siderocytes using the cytochemical method. Detection of ring sideroblasts in an amount exceeding 5% requires additional investigation to rule out MDS.

Comments: the detection of a PNH clone, regardless of the percentage of GPI-deficient cells among granulocytes, erythrocytes, and monocytes, does not rule out the diagnosis of AA.

Comments: a positive test result casts doubt on the diagnosis of AA.

1) Determination of antibodies to Treponema pallidum in blood by enzyme-linked immunosorbent assay (ELISA) or determination of antibodies to Treponema pallidum using nontreponemal tests (RPR, VDRL) (qualitative and semi-quantitative assay) in blood serum;

2) Determination of IgM and IgG antibodies to human immunodeficiency virus HIV-1 (Human immunodeficiency virus HIV 1) in blood; determination of IgM and IgG antibodies to human immunodeficiency virus HIV-2 (Human immunodeficiency virus HIV 2) in blood;

3) Determination of hepatitis B virus surface antigen (HBsAg) (Hepatitis B virus) in blood and determination of antibodies to hepatitis C virus (Hepatitis C virus) in blood;

4) Determination of antibodies to herpes simplex virus (Herpes simplex virus) in blood; determination of antibodies to human herpesvirus type 6 (Herpes-virus 6) in blood; determination of IgM and IgG antibodies to Epstein-Barr virus (Epstein - Barr virus) in blood; determination of IgM and IgG antibodies to cytomegalovirus (Cytomegalovirus) in blood.

LeR CLoE 5Level of Recommendation C (Level of Evidence — 5)

Comments: determining the colonization of the oral cavity by opportunistic antibiotic-resistant bacterial strains is necessary for selecting appropriate antibiotic therapy, as well as for potential antibiotic prophylaxis.

Comments: determining the intestinal colonization by opportunistic antibiotic-resistant bacterial strains is necessary for selecting appropriate antibiotic therapy, as well as for potential antibiotic prophylaxis.

Comments: Considering the high frequency of transfusions and the subsequent development of sensitization to donor blood components and erythrocyte chimera, packed red blood cell transfusions should be performed taking into account the phenotype.

2.4 Instrumental Diagnostics

Comments: to identify small-caliber infectious foci not visualized on radiography in accordance with the algorithms presented in Appendix A.

Comments: Abdominal ultrasound (comprehensive) is performed to assess the size of the liver and spleen and the presence of lymphadenopathy; pelvic ultrasound in women and prostate ultrasound in men are performed to rule out pathological neoplasms; peripheral and intra-abdominal lymph nodes are evaluated to rule out lymphadenopathy.

1. esophagogastroduodenoscopy (EGD);

2. colonoscopy;

3. bronchoscopy;

4. comprehensive ultrasound examination (ultrasound) of the abdominal organs, urinary tract, retroperitoneal space, comprehensive pelvic organs (transvaginal and transabdominal), joints (in the presence of hemarthrosis);

5. computed tomography (CT) of the chest, brain, and abdominal organs;

6. magnetic resonance imaging (MRI) of the brain.

LeR CLoE 5Level of Recommendation C (Level of Evidence — 5)

2.5 Other Procedures

Patients with aplastic anemia, especially with severe and very severe forms of the disease, often develop complications, including life-threatening ones, that require diagnostic examinations and treatment directly in the hematology department during the diagnosis and treatment of aplastic anemia due to the specific approaches used in hematology.

Comments: main complications of ATG therapy: allergic and anaphylactic reactions during ATG** administration and serum sickness. Allergic and anaphylactic reactions: chills, fever, erythematous or urticarial rash occur in 30–60% of patients. In these cases, the doses of administered glucocorticoids and systemic antihistamines are increased by 1.5–2 times and, if possible, ATG** administration is continued.

Bronchospasm, angioedema, and arterial hypotension develop much less frequently (in 2–3% of patients). In these cases, ATG** administration is stopped and appropriate treatment is administered.

Serum sickness usually develops on days 7–14 (days 5–20) from the start of therapy in more than 50% of patients. Fever, papular skin rashes, pruritus, polyarthralgia, myalgia, headache, and nausea are the most common symptoms of serum sickness; transient increases in aminotransferase activity, elevated blood pressure, and gastrointestinal disturbances are observed less frequently; epileptic seizures may occur in 1–2% of cases. The administration of systemic antihistamines (H1-receptor blockers) and glucocorticoids (prednisolone** 30–60 mg/day) for 1–2 weeks generally relieves serum sickness. In severe cases, plasmapheresis sessions are performed.

To prevent the development of severe allergic complications, it is recommended to strictly perform intradermal skin sensitivity tests to the drug immediately before ATG** administration.

Exacerbation of hemorrhagic syndrome during or after ATG** administration requires intensive replacement therapy with platelet concentrates and fresh frozen plasma.

Main complications of #cyclosporine** therapy

The most frequent complication is renal dysfunction associated with the nephrotoxicity of the drug; this is accompanied by increased serum creatinine, peripheral edema, and oliguria. Arterial hypertension, finger tremor, paresthesias, headaches, and, rarely, encephalopathy are also common. Gingival hyperplasia is observed in one-third of patients. Nausea, vomiting, abdominal pain, and diarrhea occur in 10–13% of cases. Hyperbilirubinemia can be detected in 30% of patients, but elevated hepatic aminotransferase activity is much less common. Electrolyte disturbances such as hyperkalemia and hypomagnesemia may occur. In some cases, gynecomastia, hypertrichosis, and allergic reactions (allergic rash) are observed. It should be noted that these complications most frequently appear against the background of the maximum dose of #ciclosporin** (10 mg/kg/day) during the first 2–3 weeks of therapy.

Toxic complications of #ciclosporin** therapy are generally managed by reducing the daily dose (by 25–50%) or temporarily discontinuing the drug. In some cases, concomitant symptomatic therapy is required.

Diagnosis of infectious complications.

Comments: Infectious complications during IST occur in the majority of patients with aplastic anemia. Bacterial infections predominate in the early stages of therapy; subsequently, as the period of granulocytopenia prolongs and immunosuppression intensifies, opportunistic infections caused by fungi (primarily Aspergillus spp.), Pneumocystis, and herpesviruses become dominant [2, 9].

Features of infectious complications recorded in aplastic anemia include a high pathogen detection rate (microbiologically documented infections account for up to 75%) and the predominance of mixed flora in the etiology of the infectious process. Infections caused by various microorganisms can be detected either at the "start" of infectious complications or arise sequentially during the treatment of these complications. The first symptom of infection is fever. Fever in the presence of granulocytopenia (neutropenia) is considered infectious if the body temperature rises above 38⁰C, persists for 2 hours, and is not associated with the administration of pyrogenic drugs.

The most frequent infectious complications developing during #ciclosporin** administration are Pneumocystis pneumonia and herpetic infections. Pulmonary involvement caused by these microorganisms is diagnosed by bronchoalveolar lavage using a comprehensive panel of tests that includes enzyme immunoassay and PCR [12, 37]

Comments: the main factor determining the development of infectious complications in hematological patients is neutropenia (neutrophils <0.5 x 10⁹/L) or leukopenia (leukocytes ≤1.0 x 10⁹/L), as well as the duration of neutropenia—the frequency of infections increases significantly when the duration of neutropenia exceeds 10 days. The risk of developing infections increases with impaired neutrophil phagocytic function, cellular and humoral immunity defects, damage to the gastrointestinal mucosa (especially grade III–IV mucositis), and the presence of a central venous catheter (CVC). The source of infection is usually the gastrointestinal tract, where active translocation of microorganisms occurs from the mucosa damaged as a result of chemotherapy. Other main portals of entry for infection in neutropenia are CVCs.

The etiological structure of pathogens in hematological patients is diverse and includes bacteria, fungi (yeast and mold), and herpesviruses. In the first 7–10 days, the infectious process is usually caused by bacteria, and as neutropenia prolongs, the risk of invasive aspergillosis increases [75]. In the etiology of bloodstream infections, gram-negative bacteria account for 49.7%, gram-positive bacteria for 42.7%, and yeast-like fungi for 7.4% [77]. The main causative agents of sepsis are Escherichia coli (17.8%), coagulase-negative staphylococci (17.4%), Enterococcus spp. (10.3%), Pseudomonas aeruginosa (7.6%), and Klebsiella pneumoniae (8.2%). In recent years, the detection of Acinetobacter spp. and Stenotrophomonas maltophilia has increased, placing them among the top five gram-negative bacteria in bloodstream infections after E. coli, K. pneumoniae, and P. aeruginosa.

The main resistance mechanisms in enterobacteria are the production of extended-spectrum beta-lactamases (ESBLs) in 40–50% of cases, and the detection of carbapenemases, predominantly in K. pneumoniae (10–30%). The resistance of P. aeruginosa to carbapenems and colistin is 40–50% and 29%, respectively, and that of Acinetobacter baumannii strains to carbapenems is 65–70% [78]. Among gram-positive bacteria, vancomycin resistance was noted in Enterococcus faecium (15%). Candida species are characterized by a decrease in the proportion of C. albicans to 30% and a wide species diversity of non-albicans Candida [77].

Characteristic signs of infections during the neutropenia/leukopenia period are

• scarcity of clinical manifestations;

• the probability of simultaneous presence of different pathogens and different localization of the infectious process;

• the possibility of the emergence of other pathogens and another localization of the infectious process as the period of neutropenia lengthens.

Fever is defined as a single recorded increase in body temperature of ≥38.0°C not associated with other causes (reactions to blood component transfusions, administered medications, tumor fever).

There is a generalizing term "febrile neutropenia", which includes all cases of febrile temperature in patients with neutropenia/leukopenia. Clinically documented infections are those that can be verified using physical or instrumental diagnostic methods in the absence of microbiological confirmation. The most frequent manifestations of clinically documented infections are pneumonia, soft tissue infection, perineal infection (including paraproctitis). Microbiological confirmation of infection during granulocytopenia is in most cases the isolation of microorganisms from blood culture.

Comments: if infection is suspected, samples of clinical material from the patient must be taken immediately. Close attention and thorough microbiological studies are required in patients taking glucocorticoids and in elderly individuals, since in this group of patients 70% of severely ill patients older than 66 years may experience septicemia with normothermia or moderate subfebrile temperature.

In neutropenia, a thorough daily examination of the patient is performed, which, along with standard therapeutic examination standards, includes the following approaches:

• active questioning of the patient regarding possible symptoms of infection, including the presence of pain along the esophagus, in the perineum;

• daily examination of the oral mucosa in neutropenia, especially the periodontium. Attention is paid to friability, mucosal edema (mucositis), presence of plaque, ulcers;

• inspection of the skin for the possible appearance of septicopyemic foci in case of fever, even in the absence of complaints (during glucocorticoid therapy, septicopyemic foci may occur at normal body temperature);

• inspection of the venous catheter insertion site;

• careful auscultation of the chest (harsh breath sounds in the absence of rales, a minimal number of moist rales in a limited area may be the initial manifestation of pneumonia);

• thorough palpation of the abdomen (the first symptoms of pseudomembranous colitis are the appearance of pain or "gurgling" upon palpation in the right iliac region (cecal area).

Comments: blood is drawn simultaneously from a vein and a CVC, or from two different veins into 2–4 bottles (aerobic/anaerobic) intended for incubation in an automated blood culture analyzer. Based on the difference in the time to positivity of blood cultures drawn simultaneously from a CVC and a vein, CVC infection may be suspected. In this case, a positive blood culture from the CVC becomes positive 2 hours or more earlier than a positive blood culture from the vein. Blood for microbiological testing is collected with maximum adherence to asepsis rules, injecting 10 ml of the patient's blood into each bottle. Inoculating a smaller volume of blood reduces the likelihood of obtaining a positive blood culture. In bloodstream infections, the isolation of coagulase-negative staphylococci and Corynebacterium spp. must be confirmed by two positive blood cultures, since these microorganisms belong to the obligate microflora, and their detection in only one of the two bottles is considered contamination of the blood samples (obligate microflora).

The central venous catheter (CVC) is removed and sent for microbiological testing when catheter-related infection is suspected (difference in the time to positivity between blood cultures drawn simultaneously from a vein and a CVC), when yeast or mold fungi are isolated from blood cultures, or when a patient with a CVC is transferred from another inpatient facility (high probability of CVC infection). For bacteriological testing, an aseptically removed distal catheter segment 5–6 cm long is sent to the laboratory in a sterile container. CVC testing is performed using a semiquantitative (Maki roll plate) or quantitative method. Diagnostic confirmation of CVC infection is the isolation of microorganisms in an amount of ≥15 colony-forming units (CFU) by semiquantitative testing, or ≥103 CFU/ml by quantitative testing.

Comments: for microbiological testing, a morning midstream urine sample is submitted, and tests are performed for various bacterial pathogens, starting with the most frequent ones in hematological practice (see below). Bacteriuria is diagnostically significant if a single microorganism is isolated in a count of ≥10³ CFU/ml. The microbiological urine test is repeated the next day if two microorganisms are isolated in counts of ≥10³ CFU/ml. Repeated isolation of the same microorganisms as in the first test confirms the presence of a urinary tract infection. In hematology, the most frequent causative agents of hospital-acquired urinary tract infections are Enterobacteriaceae, among them E. coli, followed by Enterococcus spp. and P. aeruginosa. Repeated isolation of Candida spp. from urine in patients with febrile neutropenia may indicate a high probability of disseminated invasive candidiasis. Rapid testing for antibiotic susceptibility to endotoxins is performed on all microorganisms isolated in diagnostically significant quantities in urine.

Comments: in patients with persistent febrile neutropenia and no positive blood culture, these microorganisms may be the cause of infection.

Comments: When gram-negative bacteria are isolated, species identification is performed, along with determination of susceptibility to systemic antimicrobial drugs, detection of extended-spectrum β-lactamase (ESBL) production in Enterobacteriaceae, and the modified carbapenem inactivation method (mCIM) or carbapenem inactivation method (CIM) test to determine carbapenemase production among carbapenem-resistant Enterobacteriaceae and P. aeruginosa. In addition, PCR detection of acquired carbapenemase genes of the KPC and OXA-48-like groups in oropharyngeal mucosa swabs is performed if the mCIM (or CIM) test is positive. When yeast fungi are isolated from the oropharyngeal mucosa, only species identification is performed.

Comments: taking into account the isolated microorganisms, antimicrobial therapy may be adjusted if there are no diagnostically significant results from clinically relevant samples in patients with persistent febrile neutropenia. Attention is drawn to the isolation of multidrug-resistant gram-negative bacteria – P. aeruginosa, A. baumannii, S. maltophilia, and ESBL- or carbapenemase-producing Enterobacteriaceae.

Comments: the test is performed at least twice over 5 days. Aspergillus antigen is tested before the administration of systemic antifungal drugs active against mold fungi. The test is included in the diagnostic criteria for invasive aspergillosis. Positive optical density index values for Aspergillus antigen detection are: in blood serum ≥ 0.5, in bronchoalveolar lavage fluid ≥ 1.0, in cerebrospinal fluid ≥ 1.0 [79].

Comments: the test sample is blood. The test result is considered positive at the following values: Candida antigen (mannan) ≥125 pg/mL; Candida antibodies (antimannan) ≥10 IU/mL. The test is not included in the diagnostic criteria for invasive candidiasis. The test has a high negative predictive value. Positive values do not rule out the presence of invasive candidiasis. Sensitivity and specificity are about 50–60%. Patients with mucosal colonization by Candida spp. may have positive antimannan values.

Comments: patients with aplastic anemia are at risk for this infection due to T-cell immunodeficiency. Detection of Cryptococcus spp. antigen in cerebrospinal fluid and Cryptococcus neoformans antigen in blood is performed. The test is included in the diagnostic criteria for invasive cryptococcosis. The study is carried out using a latex agglutination test (qualitative assay).

Comments: CT is performed in all cases without prior targeted chest radiography. Targeted chest radiography is considered a low-informative examination method in hematological patients; CT is preferred for diagnosing infectious complications.

Comments: clinical indications include: persistent fever (daily temperature fluctuations from 37 to 39 °C), especially in patients outside of leukopenia (for diagnosing hepatosplenic candidiasis); diagnosed pulmonary aspergillosis or mucormycosis (to rule out dissemination); to monitor previously identified changes in the diagnosis of hepatosplenic candidiasis, the follow-up study is performed no earlier than 1 month after systemic antifungal therapy, outside of leukopenia.

Comments: data from this study are particularly important in cases of microbiologically confirmed S. aureus infection and prolonged (more than 10–14 days) persistent hyperthermia, especially in patients outside of leukopenia. Transesophageal echocardiography is prescribed for persistent hyperthermia and negative transthoracic echocardiography results.

Comments: HSV in patients with hematological diseases primarily causes damage to the mucous membranes (mucositis), most frequently HSV type 1.

Comments: HHV-6 is divided into type A and type B. Viral reactivation can lead to encephalitis, bone marrow suppression, pneumonia, and cause diarrhea. HHV-6 encephalitis is a rare manifestation of infection; cases have been described following matched unrelated donor hematopoietic stem cell transplantation. In the cerebrospinal fluid of patients with HHV-6 encephalitis, an increased protein level is determined, and pleocytosis occurs in half of the cases. Brain computed tomography may be normal; abnormalities are detected on magnetic resonance imaging.

Diagnosis of other complications

Comments: the formation of gastrointestinal ulcers may manifest as dyspeptic symptoms and abdominal pain, but often runs asymptomatically, presenting with bleeding or perforation.

Comments: A characteristic feature of aseptic necrosis of the femoral head is the presence of a geographic thin line of osteosclerosis, which forms as bone tissue grows from the unaffected area into the osteonecrosis focus. In sequestration, a radiolucent band matching the shape of the focus is detected. X-ray and MRI of bones and joints are also used in planning surgical interventions in late stages of osteonecrosis with the development of deformation of the articular part of the long tubular bone. Dual-energy X-ray absorptiometry can complement instrumental diagnostics, as it allows for the detection of manifestations of systemic osteoporosis and the condition of bone tissue in the area of installed implants if patients underwent joint arthroplasty.

Comments: the studied markers can help in determining further supportive treatment tactics and prescribing specific osteoporosis therapy

• in suspected transfusion-related acute lung injury (TRALI): targeted chest X-ray, determination of antileukocyte antibodies, and determination of neutrophil cytoplasmic antibodies in the blood

• in suspected anaphylactic shock: evaluation of serum IgA levels in the recipient

• in suspected febrile non-hemolytic transfusion reaction: microbiological (culture) blood test for sterility; determination of antileukocyte antibodies, antiplatelet antibodies, and neutrophil cytoplasmic antibodies in the blood

• in suspected acute or delayed hemolysis: testing for free plasma hemoglobin levels, free and conjugated bilirubin levels in the blood, detection of hemoglobin in the urine, urine hemosiderin determination, direct antiglobulin test (direct Coombs test)

• in suspected transfusion-associated graft-versus-host disease: complete blood count, general clinical biochemical blood test (ALT, AST, alkaline phosphatase, free and conjugated bilirubin), coagulogram (exploratory hemostasis test), pathomorphological examination of skin biopsy (surgical) material (in the presence of skin erythema), molecular genetic testing of hematopoietic chimerism after unrelated bone marrow transplantation, comprehensive ultrasound examination of the abdominal organs

• in suspected post-transfusion purpura: complete blood count, determination of antileukocyte antibodies, antiplatelet antibodies

LeR CLoE 5Level of Recommendation C (Level of Evidence — 5)

3. Treatment, including drug and non-drug therapies, diet therapy, and pain management

The treatment regimen for adult patients with aplastic anemia is a combined immunosuppressive therapy administered using two main drugs with pronounced immunosuppressive effects: ATG** and #ciclosporin**, and/or hematopoietic stem cell transplantation (HSCT) [12,39–41]

Modern pathogenetic therapy for patients with aplastic anemia may include, in addition to drugs with immunosuppressive effects (ATG**, #ciclosporin**), medications aimed at activating the proliferation of hematopoietic progenitor cells while simultaneously suppressing the activation of cytotoxic cells. Numerous clinical studies have demonstrated a significant improvement in hematological parameters under the influence of eltrombopag** [41, 42]. According to its mechanism of action, eltrombopag** is a thrombopoietin receptor agonist localized not only on megakaryocytes but also on blood stem cells. Eltrombopag** binds to the transmembrane domain of thrombopoietin receptors without competing with endogenous thrombopoietin, and exhibits immunomodulatory properties through the activation of T-regulatory cells. In addition, eltrombopag** has chelating activity and promotes the removal of toxic iron from liver, heart, and other internal organ cells in iron overload among AA patients dependent on donor red blood cell transfusions [43]. The clinical use of eltrombopag** may be accompanied by a mono-, bi-, or tri-lineage hematological response in patients with refractory aplastic anemia, and its inclusion in combined aplastic anemia treatment regimens reliably increases the rate of achieving a complete response and overall patient survival [41]. The treatment regimen may also include other therapeutic interventions, in particular chelation therapy as well as splenectomy [2, 12, 44]. A tremendous role in the implementation of the treatment program for aplastic anemia patients is played by supportive transfusion therapy: transfusions of donor blood cells (packed red blood cells and platelet concentrates) [12, 17, 23].

HSCT occupies a specific place within the treatment algorithm for AA patients: the presence of an HLA-identical sibling donor, young age, a short transfusion history, and a severe form of the disease are conditions under which HSCT may be considered as the therapy of choice (first-line therapy) [45]. A significant drawback of this method is the limited possibility of application associated with the lack of a related bone marrow donor in the majority of adult patients. Nevertheless, HSCT is currently considered the therapy of choice at the first stage of treatment for young patients with severe aplastic anemia who have an HLA-identical related bone marrow donor [46, 47]. Therefore, HLA typing of patients and the search for a potential related donor must be performed already at the time of AA diagnosis. An absolute indication for HSCT in AA at any stage of the disease is the detection of unfavorable chromosomal aberrations during cytogenetic examination, primarily monosomy 7, indicating progression to MDS or AML.

The improvement of immunosuppressive therapy and the implementation of the program in the early stages of the disease have significantly increased the efficacy of aplastic anemia treatment: the probability of long-term survival in patients with aplastic anemia has increased to 80 - 90% [48, 49]. Treatment efficacy primarily depends on the timely diagnosis of aplastic anemia, the severity of the disease, the patient's age, comorbid conditions, and the feasibility of performing combined immunosuppressive therapy or HSCT already at the initial stages of treatment [12, 17, 50, 51]. The use of glucocorticoids as the primary treatment method in aplastic anemia patients, uncontrolled prolonged #ciclosporin** monotherapy (exceeding 6 months), and the unjustified use of colony-stimulating factors create unfavorable conditions for initiating combined immunosuppressive therapy and impair its efficacy [12, 13].

The analysis of the efficacy of combined immunosuppressive therapy in adult patients with aplastic anemia, presented in systematic reviews of clinical trials from 2010–2019 dedicated to the treatment of patients with aplastic anemia, makes it possible to recommend the developed treatment algorithm as the primary protocol for immunosuppressive therapy in adult patients with aplastic anemia [13, 27, 39, 52, 53].

Program-based combined IST is administered to patients with acquired AA diagnosed on the basis of a comprehensive examination, including peripheral blood analysis, myelogram (sternal puncture), evaluation of bone marrow histological specimens (bilateral iliac crest trephine biopsy), and exclusion of clonal disorders (bone marrow cell cytogenetic testing) in the absence of clinical contraindications.

3.1 Conservative therapy

Comments: HLA typing of AA patients and siblings should be performed immediately after establishing the diagnosis. If a related fully compatible donor is available, AA patients should be consulted at a transplant center.

The dose of #equine antithymocyte globulin is 20 mg/kg/day or 40 mg/kg/day (which complies with national and international treatment protocols), with a course duration of 5 or 4 days, respectively, including continuous administration of the daily dose via a 12-hour infusion. #Equine ATG should be prescribed within the framework of Protocol No. 1 (see Appendix A3) [12, 13, 17, 39, 52, 55, 56]

GCR CLOCE 4Grade of Recommendation C (Level of Evidence 4)

Comments: Taking into account data from multicenter studies demonstrating a therapeutic effect of #equine ATG superior to that of rabbit ATG, the presented recommendations include only the #equine ATG treatment protocol [57].

Due to the high risk of infectious complications during and after the treatment course, it is recommended to administer the course of #equine ATG in an aseptic single-patient room. The patient is also advised to stay in this room for 21-28 days after the end of the course.

Comments: prophylaxis of potential complications during the course begins 2 days before the start of therapy and continues for 2 weeks after the end of the course.

Comments: #cyclosporine** is prescribed starting from day 14 of the ATG** course, depending on renal function and effective blood pressure control. The initial dose of the drug is 5 mg/kg per day orally or intravenously. In patients over 60 years of age, the starting dose may be reduced to 3 mg/kg per day. Subsequently, the daily dose is adjusted based on individual pharmacokinetics and individual drug tolerance. The target trough (i.e., drawn before administration) concentration of #cyclosporine** in whole blood is 200-400 ng/mL. If renal toxicity (increased urea and creatinine), uncontrolled arterial hypertension resistant to two drugs, or hepatic toxicity develops, #cyclosporine** is stopped completely, regardless of the dose and blood concentration. After complete resolution of toxicity, #cyclosporine** is resumed at a daily dose equal to ½ of the dose that caused the toxicity. If the plasma level of #cyclosporine** rises above 400 ng/mL, the daily dose is reduced to return to the therapeutic window. The average daily dose of #cyclosporine** throughout the treatment course is determined by tolerability and the achieved concentration level. It is not recommended to increase the dose to the therapeutic level in case of poor tolerability. #Cyclosporine** therapy is continued for 2 years with a slow taper.

Comments: iron overload resulting from multiple blood transfusions is an indication for chelation therapy. If serum ferritin increases >1000 ng/mL, it is recommended to include deferasirox** in the treatment program for patients with refractory AA. Deferasirox** is administered orally in tablets at a maximum daily dose of 28 mg/kg; depending on the serum ferritin level, therapy tolerability, and comorbid pathology, the dose may be decreased or increased by 4–8 mg/kg/day. When used concomitantly with #cyclosporine**, more careful monitoring of renal function is required.

Comments: eltrombopag** therapy can be administered in the first line of therapy or in the absence of a response to a course of #equine ATG combined with #cyclosporine** when allo-HSCT is not feasible.

Comments: Eltrombopag** therapy is also possible in the presence of either single-line cytopenia (thrombocytopenia) or pancytopenia to improve the achieved treatment outcomes.

Comments: currently, #equine ATG is also the therapy of choice for a repeat course.

• Patients with confirmed refractoriness to the 1st course of ATG** therapy are recommended a consultation at a transplantation center to assess the feasibility of allogeneic hematopoietic stem cell or bone marrow transplantation from an unrelated or haploidentical donor [62, 122, 123].

GCR CLEL 5Grade of Recommendation C (Level of Evidence – 5)

Comments: in the absence of a response after 2-3 months, discuss the option of administering a course of #ATG**.

Comments: glucocorticoid monotherapy is not pathogenetic for AA.

Comments: red blood cell suspension and platelet concentrate are used; the algorithm for their use is determined by the severity of the disease, i.e., the severity of the anemia and hemorrhagic syndromes and the stage of therapy.

To manage the anemic syndrome in AA, leukocyte- and platelet-depleted red blood cell mass should be used, taking into account the erythrocyte phenotype of the donor and recipient. For a single transfusion of donor platelets, at least 6–10 doses (one dose being 0.5-0.7×10¹¹) of platelet concentrate obtained from a single donor are used; transfusions are performed with a frequency ranging from once a week to once a day depending on the following factors: administration of #ATG** therapy (on administration days), presence of bleeding, treatment with antithrombotic agents, presence of active infection, and adequacy of the transfusion increment. The use of platelet concentrates prepared by plateletpheresis can significantly reduce the number of platelet donors per recipient and lower the risk of patient alloimmunization. In severe hemorrhagic syndrome characterized by uterine or gastrointestinal bleeding accompanied by the development of DIC syndrome, fresh frozen plasma must be used.

The tactics of blood component use depend on the stage of IST.

During the preparation for the course of #equine ATG treatment, it is necessary to manage the hemorrhagic syndrome, if present, and increase the platelet count above 30.0 × 10⁹/L, and the hemoglobin level above 90.0 g/L (bleeding stops better when hemoglobin is good!!!). The frequency of transfusions is determined individually.

The tactics of blood transfusion therapy during the induction of remission on #cyclosporine** are developed individually and depend on the minimum optimal hemoglobin and platelet levels for a given patient.

The tactics of replacement transfusion therapy with blood components (donor red blood cells and platelets) in refractory AA are determined by the degree of the patient's transfusion dependency.

3.2 Surgical Treatment

Comments: in cases of ATG** intolerance, confirmed refractory AA, lack of other therapeutic options, and unavailability of bone marrow transplantation, splenectomy may be included in the treatment program.

Comments: high rate of transformation to MDS/AML.

3.3 Supportive and concomitant therapy

Comments: gastric or duodenal ulcer is one of the serious side effects of GCS therapy (included in the prevention of ATG** complications). The mechanism of the ulcerogenic action of GCS involves increased hydrochloric acid secretion in the stomach, changes in the qualitative composition of mucus, and inhibition of surface epithelium regeneration. Due to their ulcerogenic potential, antisecretory therapy is necessary when using GCS to prevent steroid ulcers.

According to a meta-analysis of 300 studies [64], gastric and duodenal ulcers scar in almost all cases if the intragastric pH is maintained above 3 for 18 hours per day. Taking this rule into account, antacids, H2-histamine receptor blockers, and proton pump inhibitors (PPIs) can currently be considered as anti-ulcer therapy. According to one of the latest meta-analyses, the use of PPIs or H2-histamine receptor blockers significantly more effectively achieves scarring of the ulcer defect and reduces the risk of recurrent bleeding. Only drugs from these two groups can achieve and maintain the necessary gastric pH environment required for the healing of gastroduodenal ulcers.

Currently, two classes of drugs are used for antisecretory purposes to prevent gastric and duodenal ulcers, including during glucocorticoid therapy: proton pump inhibitors and H2-histamine receptor blockers [65, 66].

Comments: before prescribing fluoroquinolones for prophylaxis, a rectal swab must be examined, and the test is repeated every 7 days. Prophylaxis is discontinued when systemic antibacterial drugs are prescribed for fever during neutropenia. Fluoroquinolones, such as ciprofloxacin** 0.5 g orally twice a day, are used for prophylaxis.

Comments: the drug of choice for pneumocystis pneumonia prophylaxis is #co-trimoxazole [sulfamethoxazole+trimethoprim]**, prescribed at 480 mg daily. Patients infected with Pneumocystis jirovecii must not share a room with other immunocompromised patients.

Comments: systemic antifungal drugs are prescribed 2 days before the administration of ATG** (on the day of #prednisolone** prescription).

Comments: for secondary prophylaxis, the drug that achieved cure of the invasive mycosis is prescribed starting from the 1st day of the post-course period or when the granulocyte count is ≤0.5 × 10⁹/L, as well as throughout the entire period of immunosuppressant use.

Comments: antiviral prophylaxis is used for 3–5 weeks. Switching from oral to intravenous formulation is performed in patients with mucositis.

4. Medical Rehabilitation and Sanatorium-Resort Treatment

There are no special rehabilitation methods for AA. Rehabilitation of patients with AA should be comprehensive, covering medical, social, and psychological aspects of the patient's adaptation to normal life. The scope of medical rehabilitation is developed individually for each patient by a rehabilitation specialist with the participation of a hematologist. In addition, the rehabilitation program must take into account the patient's social and psychological problems and involve social workers and medical psychologists. Rehabilitation for complications arising during the course of the disease and treatment is carried out within the framework of the respective nosologies.

5. Prevention and Dispensary Observation

There are currently no methods for the prevention of AA.

Comments: the frequency of monitoring AA patients after completion of treatment is not standardized. During the first year after completion of treatment, the patient should be monitored by a hematologist at least once every 3 months. Thereafter, the frequency of monitoring is established by the hematologist individually, depending on the patient's general condition and well-being, complications of the therapy, and the achieved response to therapy, but should not be less than once a year. During follow-up, in addition to examining the patient and taking medical history and complaints, a complete blood count with differential white blood cell count must be performed. Other diagnostic methods may be used at the discretion of the hematologist.

It should be noted that the patient may have atypical disease manifestations, as well as a combination of a specific disease with other pathologies, which may dictate changes by the attending physician in the algorithm for choosing the optimal diagnostic and treatment tactics.

6. Organization of Medical Care

Indications for elective hospitalization:

1) Administration of a course of ATG** therapy;

2) Bone marrow transplantation;

3) Prophylactic transfusions of donor blood components

4) Patient examination, including biopsies and invasive interventions, when it cannot be performed on an outpatient basis

5) Elective surgical intervention

Indications for emergency hospitalization:

1) Development of infectious and/or hemorrhagic complications;

2) Severe thrombocytopenia and/or anemia requiring emergency replacement transfusions;

Indications for discharging the patient from the hospital:

1) Following the completed ATG** course or bone marrow transplantation — outpatient follow-up;

2) Full management of hemorrhagic and/or infectious complications.

3) Completed set of diagnostic measures

7. Additional Information

none

Criteria for Evaluating the Quality of Medical Care

References

Appendix A1. Working Group Composition

1. Parovichnikova E.N., MD, DSc, General Director, National Research Center for Hematology of the Russian Ministry of Health, Moscow; Association for the Promotion of Development of Hematology, Transfusiology and Bone Marrow Transplantation «National Hematological Society».

2. Mikhailova E.A., MD, DSc, Professor, Leading Researcher, Department of Chemotherapy for Hemoblastoses and Hematopoietic Depressions, National Research Center for Hematology of the Russian Ministry of Health, Moscow; Association for the Promotion of Development of Hematology, Transfusiology and Bone Marrow Transplantation «National Hematological Society».

3. Fidarova Z.T., PhD, Head of the Department of Chemotherapy for Hemoblastoses and Hematopoietic Depressions with Bone Marrow and Hematopoietic Stem Cell Transplantation Unit, National Research Center for Hematology of the Russian Ministry of Health, Moscow; Association for the Promotion of Development of Hematology, Transfusiology and Bone Marrow Transplantation «National Hematological Society».

4. Troitskaya V.V., MD, DSc, First Deputy General Director, National Research Center for Hematology of the Russian Ministry of Health, Moscow; Association for the Promotion of Development of Hematology, Transfusiology and Bone Marrow Transplantation «National Hematological Society».

5. Gaponova T.V., MD, DSc, First Deputy General Director, National Research Center for Hematology of the Russian Ministry of Health, Moscow; Association for the Promotion of Development of Hematology, Transfusiology and Bone Marrow Transplantation «National Hematological Society».

6. Klyasova G.A., MD, DSc, Professor, Head of the Research and Clinical Laboratory of Microbiology, National Research Center for Hematology of the Russian Ministry of Health, Moscow; Association for the Promotion of Development of Hematology, Transfusiology and Bone Marrow Transplantation «National Hematological Society».

7. Kulagin A.D., MD, DSc, Prof., Director of the RM Gorbacheva Research Institute of Pediatric Hematology and Transplantology, Saint Petersburg; Association for the Promotion of Development of Hematology, Transfusiology and Bone Marrow Transplantation «National Hematological Society».

8. Lapin V.A., Hematologist, Yaroslavl Regional Clinical Hospital, Yaroslavl, Chief Hematologist of Yaroslavl Oblast; Association for the Promotion of Development of Hematology, Transfusiology and Bone Marrow Transplantation «National Hematological Society».

9. Samoilova O.S., PhD, Head of the Hematology Department, Nizhny Novgorod Oblast Clinical Hospital named after N.A. Semashko, Nizhny Novgorod; Association for the Promotion of Development of Hematology, Transfusiology and Bone Marrow Transplantation «National Hematological Society».

10. Voitsekhovsky V.V., MD, DSc, Associate Professor, Head of the Department of Hospital Therapy with a Course of Pharmacology, Amur State Medical Academy, Blagoveshchensk, Amur Oblast.

Conflict of interest: the authors declare no conflict of interest.

Appendix A2. Methodology for Developing Clinical Guidelines

Target audience of the clinical guidelines:

1. Hematologists;

2. Oncologists;

3. General practitioners.

Methods used to assess the quality and strength of evidence:

Table A2.1. Scale for assessing the levels of evidence certainty (LEC) for diagnostic methods (diagnostic interventions)

Table A2.2. Levels of Evidence (LoE) grading scale for prevention, treatment, and rehabilitation methods (preventive, therapeutic, and rehabilitative interventions)

Table A2.3. Grades of Recommendation (GoR) scale for prevention, diagnostic, treatment, and rehabilitation methods (preventive, diagnostic, therapeutic, and rehabilitative interventions)

Description of the recommendation validation method:

The preliminary version of these guidelines was reviewed by independent experts, who were asked to comment primarily on how accessible the interpretation of the evidence underlying the recommendations is for understanding.

Feedback was received from primary care physicians and general practitioners regarding the clarity of the guidelines and their assessment of the importance of the guidelines as a working tool in daily practice.

The draft version was also sent to a non-medically trained reviewer to obtain comments from a patient perspective.

Comments received from experts were carefully systematized and discussed by the chairman and members of the working group. Each item was discussed, and the resulting changes to the guidelines were recorded. If no changes were made, the reasons for refusing to make changes were recorded.

Consultation and peer review:

A preliminary version was posted for broad discussion on the website of the National Hematological Society for broad discussion and improvement of the guidelines.

The draft recommendations were also reviewed by independent experts who were asked to comment primarily on the clarity and accuracy of the interpretation of the evidence base underlying the recommendations.

Procedure for updating clinical guidelines

The mechanism for updating clinical guidelines provides for their systematic revision at least once every three years, as well as upon the emergence of new evidence-based medicine data on the diagnosis, treatment, prevention, and rehabilitation of specific diseases, or in the presence of justified additions/comments to previously approved clinical guidelines, but no more frequently than once every 6 months.

The decision to update is made by the Russian Ministry of Health based on proposals submitted by medical non-profit professional organizations. The formulated proposals must take into account the results of comprehensive assessments of medicinal products and medical devices, as well as the results of clinical testing.

Appendix A3. Reference Materials

Appendix A3.1. Protocol for the administration of ATG** in AA No. 1 [12,17,54]

¹ Before the first administration of ATG**, the patient's individual sensitivity to protein is tested using a duplicate intradermal test with tetanus antitoxin**.

² The daily dose of the drug is administered in 1200–1500 ml of physiological saline (sodium chloride solution **).

³ The first day of the course is the day of the first administration of ATG**.

Appendix B. Physician Action Algorithms

Appendix C. Patient Information

Aplastic anemia is a rare and life-threatening blood disorder caused by bone marrow dysfunction. In people with aplastic anemia, the bone marrow does not produce enough of all three types of blood cells — red blood cells, white blood cells, and platelets.

Red blood cells are essential for carrying oxygen throughout the body. White blood cells help us fight infections, germs, and other pathogens. Platelets are responsible for stopping bleeding and healing bruises.

The word «aplastic» refers to the body's inability to create new cells, resulting in the hematopoietic tissue's inability to grow or regenerate.

Aplastic anemia can occur at any age, but is most common in young people (ages 10 to 20) and older adults (over 60).

It is estimated that 100 to 150 people are diagnosed in the UK each year. This is about 2 people per 1,000,000 population. This makes aplastic anemia an extremely rare disease. The exact time of onset is unknown, and further research is needed to establish a baseline figure.

Aplastic anemia can be inherited (pertaining only to constitutional forms of AA), but most commonly it is an acquired disease that develops at a certain stage in a person's life.

It is believed that in many cases, acquired aplastic anemia is caused by damage to blood stem cells through an autoimmune reaction in the body. An autoimmune reaction occurs when the body's immune system fights its own cells, mistakenly perceiving them as damaged or defective. When this happens, bone marrow function begins to slow down, leading to a decrease in the production of all blood cell types. Autoimmune reactions may have an underlying cause—approximately one in ten people with aplastic anemia has recently had a viral infection. Other potential triggers have been identified as exposure to certain medications or chemicals, as well as radiation exposure. However, in many cases, the cause remains unknown. When there is no obvious reason for the immune system to damage stem cells in this way, a diagnosis of idiopathic aplastic anemia is established.

The most common symptoms of aplastic anemia are anemia caused by a reduced red blood cell count, accompanied by fatigue, shortness of breath, headaches, and sometimes chest pain. A lack of white blood cells can lead to infections such as sinusitis, pharyngitis, pneumonia, and intestinal infections. A low platelet count leads to a tendency for easy bleeding, such as nosebleeds or gum bleeding, and can cause unexplained bruising, blood blisters in the mouth, and severe hemorrhages, such as into the brain or intestines.

Since AA is presumed to be autoimmune in nature, immunosuppressive therapy is widely used for its treatment—that is, therapy aimed at suppressing the immune system that is "attacking" the bone marrow cells. Typically, this therapy includes antithymocyte globulin** (ATG) combined with #cyclosporine**; glucocorticoids such as methylprednisolone** can be used to prevent the side effects of ATG. The response to this therapy is usually slow: in successful cases, the bone marrow gradually recovers several weeks or months after administration of the drugs and begins producing healthy cells.

Hospitalization is usually necessary to administer a course of immunosuppressive therapy with ATG. The main complications during treatment are infections and bleeding. If there is no response to the first course of therapy, a repeated course may be administered. Immunosuppressive therapy is effective in approximately 70% of cases. Unfortunately, some patients experience relapses of the disease afterward.

Allogeneic hematopoietic stem cell transplantation, if successful, leads to a complete cure. Transplantation is particularly preferred in cases where the patient is young and has a fully matched related donor (sibling). In the absence of a related donor, the use of a matched unrelated donor or a haploidentical related donor (haploidentical transplantation) is acceptable. Previously, transplants from unrelated or partially matched donors in AA were considered very high risk, but their outcomes have improved significantly now.

During the treatment of AA, intensive blood component replacement therapy (transfusions of donor platelets and red blood cells) is often necessary. However, if a bone marrow transplant is planned, it must be kept in mind that multiple transfusions prior to transplantation increase the likelihood of graft rejection.

Prevention and treatment of bacterial, viral, and fungal infections, which pose a major danger to AA patients, are very important. Effective combinations of systemic antibacterial and systemic antifungal drugs are used for treatment, sometimes over a long period.

As adjunctive therapy, growth factors are also used—drugs that help the bone marrow produce the necessary cells. Among them is eltrombopag**, which stimulates blood stem cells and the production of all three blood cell lineages.

Without treatment, patients with severe forms of aplastic anemia die within a few months. However, with modern adequate treatment, the prognosis is quite good.

As already mentioned, immunosuppressive therapy is effective in many cases. Patients after such therapy may feel well for a long time, but some of them experience a relapse (return) of the disease. Regular check-ups, primarily blood tests, are necessary for the timely detection of a relapse.

Appendix G. Assessment Scales, Questionnaires, and Other Evaluation Tools

Not applicable.