HIV infection and AIDS

Laboratory diagnostics and routing

Establishing a diagnosis of HIV infection is impossible solely on the basis of the clinical picture or screening test results (ELISA).

• Screening: immunological blood test. It is important to remember the "seronegative window" period, when antibodies to surface antigens are not yet detectable (usually the first 3 months).
• Confirmation: the diagnosis is verified exclusively by immunoblotting (Western blot). A positive result is defined as the detection of specific antibodies to at least two of the three surface antigens of the virus.

Upon confirmation of status, the patient is referred to a specialized AIDS Center. There, counseling, immune status assessment (CD4+ T-lymphocyte count), viral load determination, and selection of highly active antiretroviral therapy (HAART) are performed.

CDC clinical and laboratory classification (1993)

Applied to adults and adolescents. The classification is built on a matrix principle, combining laboratory parameters and the clinical picture. A patient's transition to a more severe category is irreversible within the formulation of the diagnosis.

Laboratory criterion (Y-axis):

1. $\ge$ 500 cells/µL (relatively preserved immunity).
2. 200–499 cells/µL (moderate immunodeficiency).
3. < 200 cells/µL (severe immunodeficiency, laboratory criterion for AIDS).

Clinical criterion (X-axis):

• Category A: asymptomatic course, acute phase, or persistent generalized lymphadenopathy.
• Category B: symptomatic stage (diseases not included in groups A and C).
• Category C: full-blown AIDS (opportunistic infections and tumors).

The combination of these axes yields 9 categories (from A1 to C3).

Manifestations of severe immunodeficiency and the AIDS stage

Disease progression leads to depletion of the immune system. In the stages preceding AIDS, general somatic symptoms develop: weight loss of more than 10%, fever, and unexplained diarrhea lasting over 1 month. Mucous membranes are affected (hairy leukoplakia of the tongue, necrotizing ulcerative gingivitis), and severe bacterial infections occur (pneumonia, pyomyositis).

Stage IV (AIDS-defining illnesses) is characterized by generalization of processes:

• Fungal infections: Pneumocystis pneumonia, cryptococcal meningitis, disseminated candidiasis, and histoplasmosis.
• Viral infections: cytomegalovirus retinitis, progressive multifocal leukoencephalopathy, chronic Herpes simplex.
• Bacterial infections: tuberculosis (pulmonary and extrapulmonary), atypical mycobacteriosis, recurrent pneumonias.
• Protozoan infections: cerebral toxoplasmosis, cryptosporidiosis.
• Malignancies: Kaposi sarcoma, HIV-associated lymphomas.
• Direct viral effect: HIV encephalopathy and nephropathy.

Gastrointestinal and hepatic lesions

GI pathologies in HIV infection occur at all levels of the digestive tract:

1. Oral cavity and esophagus: frequently affected by Candida fungi, herpes simplex viruses, and CMV. Manifestations of Kaposi sarcoma are possible. The stomach is rarely involved (atypical localization).
2. Intestines: two variants of lesions are distinguished. The first is HIV enteropathy, caused by the direct cytopathic effect of the virus (mucosal atrophy, malabsorption syndrome). This is a diagnosis of exclusion. The second is opportunistic infections (Cryptosporidium, Microsporidia, CMV), which account for up to 40% of severe intestinal complications.
3. Perianal region: ulcerative-erosive defects of herpetic etiology and condylomata acuminata are typical.
4. Hepatobiliary system: the leading cause of lesions is viral hepatitis B and C. Iatrogenic hepatitis due to the toxicity of HAART and anti-tuberculosis drugs is also common. Cholestasis syndrome usually indicates a systemic process (mycobacteriosis, lymphoma).

Class and exam questions

What else to study on this topic

• Differential diagnosis of respiratory failure in HIV (pneumocystosis, tuberculosis, CMV, pulmonary Kaposi sarcoma).
• Syndromic approach during physical examination (stigmata of injection drug use, traces of prior Herpes zoster, seborrheic dermatitis).
• Features of serological diagnosis of toxoplasmosis (advantage of IgG over IgM in the context of HIV).
• Iatrogenic liver injury during treatment with nucleoside analogues and antituberculosis drugs.

Other topics in the section "Viral Hepatitis and HIV"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.