Diagnosis of iron deficiency states
The primary and most accurate criterion that reliably confirms both iron deficiency anemia and latent iron deficiency is the serum ferritin level.
In situations where an expanded laboratory workup is unavailable, diagnosis is based on routine parameters:
- Hemoglobin (Hb) concentration is a key indicator of anemia severity.
- Color index (CI) reflects the relative hemoglobin content in a single erythrocyte. It is calculated using the formula: `[Hb (g/L) × 3] / [first three digits of the erythrocyte count without the decimal point]` Reference values: 0.85–1.05.
- Erythrocyte morphology — peripheral blood smear microscopy reveals characteristic changes: hypochromia and microcytosis.
- Loitsy coefficient — the ratio of hematocrit (%) to hemoglobin level (%). Normally, it should be less than 3.1.
A separate method for confirming the diagnosis is ex juvantibus diagnostics (evaluation of response to therapy). The patient is prescribed oral iron preparations. In true iron deficiency, after 10–14 days, the following is observed:
- Daily Hb increase of 1–4 g/L.
- Development of a reticulocyte crisis (reticulocyte count increases to 3–4%).
Early anemia of prematurity: general characteristics
This condition is considered a benign ("physiological") anemia with a complex multifactorial pathogenesis.
The disease manifests in the 1st to 2nd month of life and occurs in more than 50% of preterm infants. In full-term infants, this pathology develops significantly less frequently and, as a rule, against the background of an burdened premorbid background.
The clinical presentation is usually sparse. The main symptom is pallor of the skin, which becomes visually noticeable when the Hb level drops to 80 g/L.
The laboratory picture differs from classic IDA: normochromic or hyperchromic normoregenerative anemia is observed, which often reaches a severe degree.
Pathogenesis of anemia in preterm infants
The development of the pathology is caused by a combination of five key factors:
- Hemolytic factor. Enhanced "physiological" breakdown of erythrocytes containing fetal hemoglobin (HbF) occurs.
- Morphofunctional immaturity of the red bone marrow.
- Decreased erythropoietin production. This is a direct consequence of hyperoxia, which the newborn suddenly experiences at birth.
- Nutrient and trace element deficiency. Normally, the deposition of proteins, copper, cobalt, vitamins C, E, and B-group occurs in the last 2 months of gestation. Preterm infants experience a shortage of these. These substances are critically important for the absorption and transport of iron, its fixation in heme, and the maintenance of erythrocyte membrane stability.
- Latent iron deficiency. Iron stores in storage sites are initially reduced, but at the initial stage, this is compensated for by the iron released during hemolysis.
Latent deficiency is indicated by specific markers: decreased serum iron, the appearance of a pool of microcytes and hypochromic erythrocytes, and a decrease in the number of siderocytes in bone marrow punctate.
As neonatal iron stores are completely depleted, early anemia naturally transforms into late anemia of prematurity.
Treatment approaches
Therapy for early anemia in premature infants has historically presented certain difficulties:
- Historical approach. Previously, the main method of correction was blood transfusions (packed red blood cell transfusion), which were used exclusively according to strict vital indications.
- Modern approach. Currently, recombinant human erythropoietin preparations (e.g., epoetin beta) are successfully used, which makes it possible to effectively stimulate the child's own erythropoiesis.
How to easily remember the color index (CI) calculation: "Hemoglobin divided by three, and erythrocytes without decimals." Multiply Hb by 3 and divide by the first three digits of the erythrocyte count.
Class and exam questions
Which parameter is the baseline for diagnosing IDA?
The gold standard and baseline criterion for confirming iron deficiency anemia and latent deficiency is the serum ferritin level.
What does ex juvantibus diagnostics involve in iron deficiency?
The patient is prescribed oral iron preparations. If after 10–14 days hemoglobin begins to rise by 1–4 g/L per day and a reticulocyte crisis occurs (up to 3–4%), the diagnosis is considered confirmed.
Why do preterm infants have decreased erythropoietin production?
This is a direct consequence of hyperoxia (excessive oxygen exposure), which the child's body abruptly encounters at birth.
How to detect latent iron deficiency in infants against the background of hemolysis?
Markers include the appearance of microcytes and hypochromic erythrocytes in a blood smear, a drop in serum iron, and a decrease in the number of siderocytes in bone marrow punctate.
What else to study on this topic
- Calculation and clinical significance of the Loitsy coefficient
- The role of cofactors (copper, cobalt, vitamins) in heme iron fixation
- Mechanisms of physiological erythrocyte hemolysis involving HbF
- Transformation of early anemia of prematurity into late anemia: transition criteria
- Pharmacodynamics of recombinant human erythropoietin
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