Erythrocyte hypochromia

Main blood parameters in hypochromia

For the primary detection of erythrocyte hypochromia, competent interpretation of complete blood count (CBC) indicators plays a key role. If this hematopoiesis disorder is suspected, a specialist needs a thorough assessment of the following basic red blood cell parameters:

• Total hemoglobin level (Hb).
• Hematocrit (Htc).
• Mean corpuscular volume (MCV).
• Mean corpuscular hemoglobin concentration (MCHC).

If the study results show a decrease in Hb levels, as well as a drop in MCV and/or MCHC indices, this is direct evidence of the development of hypochromia. In such a clinical situation, a crucial and urgent step is targeted screening of the patient for iron deficiency, as it is the most frequent cause of insufficiently pigmented erythrocytes.

Hypochromia against the background of systemic inflammation

Anemia accompanying an active inflammatory process and a strained immune response often has a hypochromic character. At the same time, one cannot be limited to an isolated assessment of erythrocytes alone. The laboratory picture of inflammation is usually complex and complemented by a number of characteristic pathological shifts.

First of all, the complete blood count records pronounced neutrophilic leukocytosis and a significant acceleration of the erythrocyte sedimentation rate (ESR). Biochemical markers of inflammation demonstrate dysproteinemia: there is a noticeable increase in $\alpha_2$-globulin and $\gamma$-globulin fractions. Simultaneously, there is an active growth of classical acute-phase indicators, such as C-reactive protein (CRP) and fibrinogen. Within specific laboratory diagnostics, the detection of rheumatoid factor (RF) is of great importance, the appearance of which significantly helps in verifying the diagnosis.

Differential diagnosis with normochromic conditions

Far from every decrease in hemoglobin level occurs with phenomena of hypochromia. It is extremely important to be able to distinguish hypochromic conditions from normochromic anemias, which are typical for completely different severe pathologies and systemic lesions.

For example, in infective endocarditis, anemia is strictly normochromic. Laboratory manifestations of this disease are quite extensive: there is an increase in lactate, metabolic acidosis, and an increase in serum transaminases. The blood test may show both leukocytosis and leukopenia with thrombocytopenia, as well as accelerated ESR. In 50% of patients with endocarditis, rheumatoid factor is elevated, positive CRP and hypergammaglobulinemia are noted. Urinalysis reveals microhematuria with or without proteinuria. Biochemical study demonstrates hypoalbuminemia, azotemia, and elevated creatinine, while the coagulogram shows an increased prothrombin time, a decreased Quick's prothrombin index, and an increase in fibrinogen.

Another striking example is acquired pure red cell aplasia (PRCA). When PRCA is suspected, all patients are prescribed an extended CBC with the study of erythrocyte and reticulocyte levels and cell size determination to verify the diagnosis. PRCA is characterized by isolated normochromic and normocytic anemia. At the same time, the reticulocyte count is sharply reduced (typically < 10,000 cells/$\mu$L; in relative terms < 1%). If PRCA is idiopathic, the platelet and leukocyte counts and leukocyte formula remain unchanged. In secondary PRCA, these indicators depend on the nature of the underlying disease.

Biochemical search for the causes of anemic syndrome

To finally confirm the nature of the developed anemia and perform accurate differential diagnosis with pathologies of a different etiology, all patients are prescribed an expanded complex of biochemical blood tests. This diagnostic stage makes it possible to reliably exclude other types of anemia:

1. To rule out hemolytic anemias, pigment metabolism is studied: total bilirubin, free (indirect) and conjugated (direct) bilirubin levels are assessed, as well as the activity of the lactate dehydrogenase (LDH) enzyme.
2. To rule out renal anemia, renal function assessment is required: creatinine and urea concentrations are checked, and the level of erythropoietin in the blood is determined.
3. To rule out deficiency hyporegenerative anemias (which should also be distinguished from hypochromic iron deficiency states), the concentration of vitamin B12 (cyanocobalamin) and the serum folic acid level are measured.

Class and exam questions

What else to study on this topic

• Laboratory signs of systemic inflammation (CRP, dysproteinemia, fibrinogen)
• Infective endocarditis: metabolic and coagulation shifts
• Pure red cell aplasia (PRCA): idiopathic and secondary forms
• Differential diagnosis of hemolytic and renal anemias based on biochemical analysis
• The role of rheumatoid factor in the diagnosis of inflammatory and infectious processes

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