What tests are included in a standard haematinic (iron deficiency) screen?

Standard Haematinic Screen Components

A standard haematinic screen should include a complete blood count (CBC) with red cell indices, serum ferritin, transferrin saturation (or serum iron and total iron-binding capacity), and vitamin B12 and folate levels. 1, 2

Core Components

Hematological Tests (Red Blood Cell Parameters)

• Hemoglobin concentration and hematocrit are the most commonly used screening tests due to their low cost and ease of performance, though they are late indicators of iron deficiency that only become abnormal in advanced stages 3

• Mean corpuscular volume (MCV) measures the average red blood cell size and is essential for classifying anemia as microcytic (<80 fL), normocytic (80-100 fL), or macrocytic (>100 fL) 1

• Red cell distribution width (RDW) is critical for detecting mixed deficiencies; an elevated RDW (>14.0%) with microcytosis strongly suggests iron deficiency anemia 1

• Mean corpuscular hemoglobin (MCH) provides sensitive indication of iron deficiency in the absence of chronic disease or hemoglobinopathy 2

• Reticulocyte count helps distinguish between production defects (low/normal reticulocytes) and hemolysis or blood loss (elevated reticulocytes) 3, 1

Biochemical Tests for Iron Status

• Serum ferritin is the most powerful single test for diagnosing iron deficiency, with levels <30 μg/L indicating iron deficiency in non-inflammatory states 1, 2

• Transferrin saturation (calculated from serum iron and total iron-binding capacity) represents iron available for erythropoiesis, with <20% indicating functional or absolute iron deficiency 3, 1

• Serum iron and total iron-binding capacity (TIBC) are measured together to calculate transferrin saturation 3

Vitamin Deficiency Tests

• Vitamin B12 and folate levels must be included as deficiencies of these haematinics cause anemia and are common in gastrointestinal disease 4, 5

Important Caveats

Interpretation Challenges

• Ferritin is an acute-phase reactant and may be falsely elevated in inflammatory conditions; use a higher threshold (<100 μg/L) to diagnose iron deficiency when inflammation is present 3, 2

• C-reactive protein (CRP) should be measured alongside ferritin to assess for inflammation that could confound interpretation 1

• Hemoglobin and hematocrit alone are insufficient for diagnosing iron deficiency, as they only decrease with severe depletion and many iron-depleted individuals will have normal values 6

Advanced Testing When Needed

• Erythrocyte protoporphyrin concentration detects earlier changes in iron status than hemoglobin or hematocrit 3

• Soluble transferrin receptor (sTfR) may help distinguish iron deficiency anemia from anemia of chronic disease, particularly in patients with liver disease or inflammatory conditions 1, 7

• Percent hypochromic red blood cells (PHRBC) and content of hemoglobin in reticulocytes (CHr) are specialized tests with high sensitivity and specificity for functional iron deficiency, though they require expensive equipment and are not widely available 3

Common Pitfalls to Avoid

• Do not rely solely on MCV for classification, as coexisting conditions may neutralize MCV changes (e.g., concurrent iron and B12 deficiency may produce normal MCV) 1

• Do not order CBC alone without iron studies, as this misses many cases of iron depletion before anemia develops 6

• Do not misinterpret ferritin without considering inflammatory status, as this leads to incorrect diagnosis in patients with chronic disease 1, 2

• Do not fail to investigate underlying causes of deficiencies, particularly gastrointestinal bleeding in iron deficiency 1