Additional diagnostic methods in hematology

Laboratory evaluation of iron metabolism

A complete blood count is insufficient for the precise diagnosis of anemias; a detailed assessment of iron metabolism is required. Key biochemical markers include:

• Serum iron: the normal range is 14.3–28 µmol/L.
• Transferrin and TIBC: free transferrin serves as the primary transport protein. Its level directly reflects total iron-binding capacity (TIBC, normal range 55–65 µmol/L). In iron deficiency anemia (IDA), transferrin saturation drops to 15% or lower.
• Ferritin: responsible for intracellular storage (depot) of iron. Its plasma level is determined via radioimmunoassay. If the value falls below 10 mcg/L, it confirms the diagnosis of IDA. It is important to note that during iron supplementation, ferritin levels react with a delay, starting to rise only after 2–3 weeks.

Bone marrow and erythropoiesis examination

When non-invasive methods fail to clarify the cause of hemoglobin decline, invasive evaluation is used. The material is obtained by puncturing spongy bones. Access is achieved via two routes: through the sternum (sternal puncture) or through the iliac crest (trephine biopsy).

Indications for the procedure:

1. Undiagnosed anemias.
2. Ruling out or confirming oncohematological pathology (e.g., leukemias).
3. Presence of pancytopenia.
4. Screening for bone marrow metastases of solid tumors.

Simultaneously, the functional state of erythropoiesis is assessed. Normal erythrocyte maturation relies on humoral regulation (erythropoietin production by the kidneys), adequate substrate supply (tissue iron stores, vitamin $B_{12}$ and folic acid for precursor DNA synthesis), and preserved proliferative capacity of the bone marrow itself as the target organ.

Specific leukocyte diagnostics

To accurately verify the type of malignant cells (mycoses, leukemias), highly specialized technologies are used:

• Cytochemical examination. Based on detecting specific enzymes in leukocyte granules, such as peroxidase or alkaline phosphatase. This allows for determining the differentiation stage and lineage affiliation of the cells.
• Immunophenotyping. A high-precision method for identifying specific lymphocyte subsets using monoclonal antibodies that bind to surface membrane proteins.
• Cytogenetic examination. Analyzes the chromosomal set of blood cells to detect morphological and quantitative aberrations. A classic example is the detection of the "Philadelphia chromosome," which is a key diagnostic marker for chronic myeloid leukemia.

Hemostasis system evaluation

Blood coagulation testing (coagulogram) is essential for diagnosing coagulopathies and monitoring antiplatelet and anticoagulant therapy.

Platelet compartment Platelet counts are determined in a complete blood count, while their functions (adhesion—surface attachment, and aggregation—clumping together) are assessed instrumentally. General tests are also performed: clot retraction (clot contraction time) and Duke's bleeding time (measuring the duration of bleeding from an earlobe puncture).

Coagulation cascade

• Blood clotting time (in vitro). Measured from the moment blood contacts a foreign surface until clot formation. Used for daily monitoring during direct anticoagulant (heparin) therapy for dose adjustment.
• aPTT (activated partial thromboplastin time). A more modern test of the coagulation system activity, also used to monitor heparin therapy.
• Prothrombin time. Reflects the rate of prothrombin conversion to thrombin (time of plasma clot formation upon addition of calcium and thromboplastin).
• PTI (prothrombin index). The ratio of standard prothrombin time to the patient's prothrombin time, expressed as a percentage.
• INR (international normalized ratio). A calculated index for standardizing results (especially during indirect anticoagulant therapy). It is the ratio of the patient's prothrombin time to the control, raised to the power of the international sensitivity index (a parameter comparing the reagent used with standard thromboplastin).

Additionally, as part of the coagulogram, fibrinogen levels and the activity of individual clotting factors are measured.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Radioimmunoassay for ferritin: working principle.
• Differences in the execution technique of sternal puncture and trephine biopsy.
• The role of folic acid and vitamin B12 in the DNA synthesis of erythrocyte precursors.
• The mechanism of action of monoclonal antibodies in immunophenotyping.
• Detailed algorithm for calculating INR and the thromboplastin sensitivity index.

Other topics in the "Blood System" section

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