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.
| Iron Deficiency Anaemia | Anaemia of Chronic Disease | Acute Phase Reaction | Iron Overload |
| Serum Iron | ⬇ Low | ⬇ Low | ⬇ Low | ⬆ High |
| Transferrin / TIBC | ⬆ High | ⬇ Low | ⬇ Low | ⬇/↔ Low/Normal |
| Transferrin Saturation | ⬇ Low | ⬇ Low | ⬇ Low | ⬆ High |
| Ferritin | ⬇ Low | ↔ Normal (↑ if APR) | ⬆ High | ⬆ High |
| Soluble Transferrin Receptor | ⬆ High | ↔ Normal | ↔ Normal | ⬇ 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.
