Key parameters of the complete blood count
The clinical blood test evaluates hemoglobin, erythrocytes, reticulocytes, platelets, leukocyte differential (band and segmented neutrophils, eosinophils, basophils, lymphocytes, monocytes), and ESR. The latter parameter is low-specificity and practically unused in differential diagnosis.
Reference ranges vary between laboratories, so one should rely on the specific reference values provided by the lab report. For practical work, it is sufficient to remember that the color index averages 0.85–0.95, and reticulocytes make up 0.6–2 %.
Morphological cell changes
- Gumprecht shadows (Botkin-Gumprecht cells) are chromatin remnants of destroyed leukocytes; a marker of increased lymphocyte fragility, characteristic of chronic lymphocytic leukemia.
- Howell-Jolly bodies and Cabot rings are nuclear remnants in erythrocytes; typical of vitamin B12-deficiency anemia and associated with impaired cell division.
- Toxic granulation of neutrophils is a sign of severe infection or bone marrow exhaustion in severe diseases.
- Anisocytosis is variation in erythrocyte size (micro- and macrocytosis), and poikilocytosis is variation in erythrocyte shape.
- Normoblasts in the blood are acceptable in significant blood loss, whereas megaloblasts always indicate abnormal hematopoiesis.
Anemias: classification by color index and regeneration
Anemia is a decrease in hemoglobin levels (and, as a rule, erythrocytes) per unit of blood volume. Hemoglobin is the defining parameter: hemoconcentration or hemodilution can distort the picture.
By color index, anemias are divided into:
- hypochromic (color index below 0.85) — characteristic of iron-deficiency and chronic posthemorrhagic anemia;
- normochromic — typical of acute posthemorrhagic anemia;
- hyperchromic (color index above normal) — indicate vitamin B12-deficiency anemia.
Based on the bone marrow's capacity for erythroid regeneration, the following are distinguished:
- regenerative anemia — reticulocytes within 0.6–2 %;
- hyperregenerative — reticulocytes above normal (massive release of young forms during blood loss);
- hyporegenerative — reticulocytes below 0.6 %;
- aregenerative — reticulocytes are practically absent;
- aplastic — diagnosis requires examination of the bone marrow aspirate.
Terminology of cellular composition changes
Suffixes -penia (decrease) and -cytosis/-philia (increase) are used to describe deviations: thrombocytopenia and thrombocytosis, leukopenia and leukocytosis, lymphocytopenia and lymphocytosis, neutropenia and neutrophilia. Changes may be absolute or relative, but for the propaedeutics course it is sufficient to indicate the fact of the shift.
Differential diagnosis of leukemias
Leukemias are divided into acute and chronic; classification is determined by the leukocyte differential picture.
- Acute leukemia is characterized by a large number of blast cells (myeloblasts or lymphoblasts) and the presence of a leukemic hiatus (leukemic gap) — the absence of intermediate maturation forms (metamyelocytes) with persistent blasts and mature neutrophils.
- Chronic myelogenous leukemia is accompanied by a moderate increase in myelocytes and metamyelocytes without a gap, as well as a basophil-eosinophil association — a simultaneous increase in eosinophils and basophils.
- Chronic lymphocytic leukemia is diagnosed by marked lymphocytosis and the presence of Gumprecht shadows.
True leukemia must be distinguished from a leukemoid reaction — a reactive release of myelocytes and their precursors into the bloodstream during stress, severe infections, or cardiac pathology. This is a physiological response variant that does not require an oncohematological diagnosis.
Reactive changes and infectious shifts
Chronic infections are typically characterized by a combination of leukopenia, neutropenia, relative lymphocytosis, and toxic granulation of neutrophils. Isolated eosinophilia is characteristic of allergic reactions and helminthiases (e.g., ascariasis). The appearance of normoblasts in peripheral blood with preserved bone marrow function is regarded as a compensatory response to acute blood loss.
Hemogram evaluation algorithm
- Evaluate hemoglobin and erythrocyte levels — establish the presence of anemia.
- Determine the type of anemia based on the color index and reticulocytes.
- Analyze the platelet and leukocyte counts.
- Examine the leukocyte differential: presence of blasts, left shift, leukemic gap, basophil-eosinophil association.
- Consider the morphological features of erythrocytes and neutrophils (Howell-Jolly bodies, Cabot rings, Gumprecht shadows, toxic granulation).
- Formulate a conclusion: type of anemia, leukemia (acute/chronic, myeloid/lymphoid), or reactive state.
Key points
- The diagnosis of anemia is established primarily by the hemoglobin level.
- Hypochromic anemia is iron-deficiency; hyperchromic is vitamin B12-deficiency.
- Howell-Jolly bodies and Cabot rings are markers of vitamin B12-deficiency anemia.
- Gumprecht shadows are characteristic of chronic lymphocytic leukemia.
- The leukemic gap is a key sign of acute leukemia.
- The basophil-eosinophil association is typical of chronic myelogenous leukemia.
- A leukemoid reaction is a reactive state simulating leukemia.
- Isolated eosinophilia indicates allergy or helminthiasis.