From the Guidelines
Iron deficiency anemia is diagnosed using labs that measure ferritin, transferrin saturation, and other iron parameters.
Key Lab Tests
- Ferritin: a serum ferritin level < 45 ng/mL is indicative of iron deficiency anemia in patients without inflammation, as recommended by the AGA 1
- Transferrin saturation (TfS): a TfS level < 16% is also a sensitive marker of iron deficiency, although it has a low specificity of only 40-50% 1
- Serum iron: measures the amount of iron immediately available for hemoglobin synthesis
- Total iron-binding capacity (TIBC): measures the total amount of iron that can be bound by transferrin
Special Considerations
- In patients with inflammation, the lower limit of serum ferritin consistent with normal iron stores should be increased to 100 μg/L, and hypoferraemia should be considered likely if TfS is < 16% and serum ferritin is between 30 and 100 g/L 1
- The determination of soluble transferrin receptor (sTfR) can help to differentiate between iron deficiency and anemia of chronic disease (ACD) 1
- In patients with chronic kidney disease, iron deficiency is common and should be evaluated using serum ferritin, TfS, and other iron parameters 1
From the Research
Labs that Diagnose Iron Deficiency Anemia
The following labs are used to diagnose iron deficiency anemia:
- Complete Blood Count (CBC) with reticulocyte hemoglobin content (CHr) 2
- Bone marrow examination, although it is a painful, invasive, and costly procedure 2
- Serum ferritin measurement, which is the most important analysis in the study of iron deficiency 3, 4
- Soluble transferrin receptor (sTfR) measurement, which is a good supplement to ferritin measurement and is relatively unaffected by inflammation 3, 4
- Serum iron, transferrin, and transferrin saturation measurements, although they provide little additional information compared to ferritin measurement 3
- Reticulocyte Hb content (CHr) determination, which is an early parameter of iron deficiency erythropoiesis 4
- Hepcidin measurements, which appear to be an interesting marker for diagnosing iron deficiency and identifying individuals in need of iron supplementation 4
- C-reactive protein (CRP) measurement, which is used to detect simultaneous acute infection and/or inflammation 4
Diagnostic Criteria
The diagnostic criteria for iron deficiency anemia include:
- Low hemoglobin level, typically two standard deviations below normal 5
- Low serum ferritin level, with a cutoff value that varies depending on the population and the presence of inflammation 3, 4
- Low reticulocyte hemoglobin content (CHr) 2
- Elevated soluble transferrin receptor (sTfR) level 3, 4
Laboratory Tests
The laboratory tests used to diagnose iron deficiency anemia include: