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If haemoglobin (Hb) is low (anaemia), blood iron studies can identify if this is caused by iron deficiency. To ensure appropriate prescribing of iron, the following information on the diagnosis of IDA should be considered.
- Serum ferritin (SF) is the most useful test in confirming the diagnosis of iron deficiency.
- If Hb <130g/L in males or Hb <115g/L in females and SF <45micrograms/L this is diagnostic of IDA and no further iron studies are required.
- SF levels can be elevated by inflammatory processes and can mask iron deficiency.
- SF >150micrograms/L generally rules out IDA even in the presence of inflammatory disease and no further iron studies are required. If there is uncertainty, consider monitoring Hb in response to a trial of oral iron.
- Serum iron, transferrin (TF) and transferrin saturation (TSAT) are labile measurements and not reliable indicators of low iron stores, however they are useful for investigating high SF and possible iron overload.
- TSAT may be used in investigation of anaemia in heart failure, renal failure, elderly patients and those with inflammatory disease where SF is non-diagnostic (high transferrin or TSAT <16% can be suggestive of iron deficiency but should not be considered in isolation, refer to flowchart in full guideline).
