Initial tests
IDA may be effectively diagnosed by a full blood examination and serum ferritin level in most cases. Serum iron levels should not be used to diagnose iron deficiency.
The following table provides details as to how a full blood examination and serum ferritin can assist in the diagnosis of IDA:
Hb g/L value is required to assess severity of anaemia.
Iron deficiency can occur without anaemia.
Ferritin is required to confirm diagnosis.
Red cell indices such as low MCV and MCH may suggest iron deficiency but can be normal.
A constellation of the following findings on full blood count is highly suggestive of iron deficiency anaemia:
- anaemia
- microcytosis
- hypochromia
Serum ferritin levels and iron status in adults:
- <15 μg/L is diagnostic of iron deficiency
- 15–30 μg/L is highly suggestive of iron deficiency
- >15 μg/L but <100 μg/L possible iron deficiency
- >100 μg/L iron deficiency unlikely (but consider functional iron deficiency)*
Lower thresholds have been used in children, from 10–12 μg/L.
This can result in misleading elevated ferritin levels in iron deficient patients with coexisting systemic illness.
Markers such as C-reactive protein may help identify coexisting inflammation.
*Functional iron deficiency is when iron cannot be mobilised for erythropoiesis despite adequate stores. It is most commonly seen in patients with end-stage kidney disease or inflammatory conditions such as rheumatoid arthritis.
Additional tests
Additional tests may be considered when the clinical features and haematology profile are suggestive of iron deficiency, but ferritin is normal. Consider consulting with a pathologist or haematologist before ordering these additional tests.
The following table summarises additional tests which may be of assistance in diagnosis of iron deficiency:
Serum iron is often reported but only reflects recent intake and is not useful in the diagnosis of iron deficiency.
These tests are recommended when serum ferritin is reported as normal or high and:
- iron deficiency is suspected clinically, or
- patient has kidney failure, or
- chronic infection, inflammation or malignancy is present
sTfR/log ferritin ratio is highly correlated with body iron stores.
sTfR estimation is limited by variability in interassay cut-offs, availability and slow turnaround in some laboratories.
sTfR is not routinely available.
Reliant on compliance.
Increase in haemoglobin of 10–20 g/L in 2–4 weeks is diagnostic of iron deficiency.
References
British Columbia - Gastroenterological Society of
Australia Sydney ,Australia - Pasricha SR, Flecknoe-Brown SC, Allen KJ, Gibson PR, McMahon LP, Olynyk JK, et al. Diagnosis and management of iron deficiency anaemia: a clinical update. MJA 2010;193:525–532. Available from: http://www.mja.com.au.
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