Makindo Medical Notes

Related Subjects: |Ferritin |CEA |ESR |CRP |ALP |LDH |HbA1c |Alpha Fetoprotein |Anti-Hu ab |Anti-Yo ab |Biochemical Lab values

🩸 Iron studies help differentiate iron deficiency anaemia (IDA) from anaemia of chronic disease (AOCD), acute phase reactions, and iron overload.
👉 IDA = ferritin low, TIBC/transferrin high. 👉 AOCD = ferritin normal/high (APR), iron low, TIBC low.

🔹 Ferritin

• Main intracellular storage form of iron – each molecule can hold ~4500 Fe atoms.
• Acute phase reactant: can be elevated in infection/inflammation even if iron deficient.
• Diagnostic cut-offs: Ferritin <15 μg/L is very specific for IDA; <30 μg/L often used in practice (higher cut-offs in chronic inflammation/CKD).
• >1000 μg/L → consider haemochromatosis or chronic liver disease.

🔹 Serum Iron

• Reflects ferric (Fe³⁺) ions bound to transferrin.
• Highly variable — affected by meals, diurnal rhythm, and illness → **not reliable in isolation**.
• <10 μmol/L = likely deficiency; >30 μmol/L = overload.

🔹 Transferrin

• Iron-transport protein (apotransferrin) carrying 1–2 Fe atoms.
• ⬆ Rises in IDA to maximise uptake.
• ⬇ Falls in liver disease, inflammation, nephrotic syndrome.

🔹 Transferrin Saturation

• Calculated: (Serum iron ÷ TIBC) × 100.
• Normal ≈ 30% saturated.
• <16% = iron deficiency. >45% = possible overload. >55% in men / >50% in women = screen for haemochromatosis.

🔹 Total Iron Binding Capacity (TIBC)

• Reflects **binding site availability** on transferrin.
• ⬆ High in IDA (>70 μmol/L). ⬇ Low in overload (<45 μmol/L).

📌 Diagnostic Criteria for Iron Deficiency Anaemia

• Ferritin <15 μg/L (or <30 μg/L depending on guidelines).
• Transferrin saturation <16%.
• Hb below reference (WHO cut-offs: <120 g/L women, <130 g/L men ≥15 yrs).
• Therapeutic trial: Hb rise ≥1 g/dL after ~8 weeks of iron therapy supports diagnosis.

💡 Teaching pearl: Ferritin is the most reliable single marker of iron stores. Always interpret in context: - Low ferritin = IDA. - Normal ferritin does not exclude IDA if inflammation, CKD, or malignancy present → check transferrin saturation and CRP.