Iron Deficiency Anemia: Test and Diagnosis

1st order laboratory parameters – obligatory laboratory tests.

• Small blood count [microcytic hypochromic anemia:
  • MCV (mean corpuscular volume; mean individual red cell volume/volume of a single red blood cell) ↓ → microcytic
  • MCH (engl. mean corpuscular hemoglobin; mean corpuscular hemoglobin (= mean hemoglobin content per erythrocyte)) ↓ → hypochromic
  • MCHC (engl. mean corpuscular hemoglobin concentration; mean corpuscular hemoglobin concentration: mean hemoglobin concentration of the hematocrit (the erythrocyte mass)) ↓]
• Differential blood count
• Red cell morphology (blood smear) [hypochromia, microcytosis, anulocytes].
• Ferritin (iron storage protein) [↓↓]
• Folic acid
• Vitamin B12
• Iron [serum iron ↓]
• Reticulocytes (“young erythrocytes”) – used to differentiate into hypo- and hyperregenerative anemia [iron deficiency anemia: normal; bleeding anemia: ↑]
• Inflammatory parameters – CRP (C-reactive protein) or ESR (erythrocyte sedimentation rate).
• Urine status (rapid test for: pH, leukocytes, nitrite, protein, glucose, ketone, urobilinogen, bilirubin, blood), sediment, if necessary urine culture (pathogen detection and resistogram, that is, testing suitable antibiotics for sensitivity / resistance).
• Test for occult (not visible) blood in the stool.

Laboratory parameters 2nd order – depending on the results of the history, physical examination, etc. – for differential diagnostic clarification.

• Transferrin (iron transport protein) [↑]
• Transferrin saturation [↓; transferrin saturation < 20% has a high sensitivity (percentage of diseased patients in whom the disease is detected by the use of the test, i.e., a positive test result occurs) of 90% for the detection of iron deficiency states, but only a low specificity (probability that actually healthy persons who do not suffer from the disease in question are also detected as healthy in the test) of 40-50%]
• Transferrin receptors (Soluble Transferrin Receptors, sTfR): concentration of sTfR in serum is an indicator of iron supply to erythropoiesis.
• Zinc protoporphyrin (ZPP): if iron deficiency does not provide sufficient iron for incorporation into protoporphyrin 9 for heme formation, zinc is incorporated as a substitute.
• Iron absorption test – if iron absorption disorder is suspectedProcedure: If serum iron increases by at least 9 μmol/l within 2 hours after oral administration of 200 mg of divalent iron in a fasting, recumbent patient, intact iron absorption is present. In the absence of an increase after 4 hours, iron reabsorption disorder is present.
• Haptoglobin [iron deficiency anemia: normal] – due todiagnostic [hemolytic anemias: ↓] and course assessment of hemolytic diseases.
• Lactate dehydrogenase (LDH).
• Renal parameters – urea, creatinine, uric acid.
• Liver parameters – alanine aminotransferase (ALT, GPT), aspartate aminotransferase (AST, GOT), glutamate dehydrogenase (GLDH), gamma-glutamyl transferase (γ-GT, gamma-GT; GGT), alkaline phosphatase, bilirubin.
• Thyroid parameters – TSH (thyroid-stimulating hormone).
• Bone marrow biopsy

Further notes

• Often to be differentiated from iron deficiency anemia is differential diagnosis of bleeding anemia. For this, a decreased number of erythrocytes (red blood cells) and a decreased hemoglobin concentration (blood pigment) in the blood is characteristic. Furthermore, peripheral reticulocytosis (increased occurrence of immature erythrocyte precursors (reticulocytes) in the blood) occurs in bleeding anemia. Bleeding anemia is caused by acute blood loss. The source of bleeding is primarily genital or gastrointestinal.

Stages of iron deficiency

Legend

• Soluble Transferrin Receptors (sTfR): concentration of sTfR in serum is an indicator of iron supply to erythropoiesis.
• Zinc protoporphyrin (ZPP): if iron deficiency does not provide sufficient iron for incorporation into protoporphyrin 9 for heme formation, zinc is incorporated as a substitute.