From the Guidelines
To diagnose iron deficiency anemia, serum ferritin is the single most useful marker and should be confirmed by iron studies prior to investigation, with other blood tests such as transferrin saturation being helpful if a false-normal ferritin is suspected. When evaluating patients for iron deficiency anemia, it's crucial to start with a definition of anemia as a hemoglobin (Hb) concentration below the lower limit of normal for the relevant population and laboratory performing the test 1.
Key Laboratory Tests
- A complete blood count (CBC) to assess hemoglobin, hematocrit, and red blood cell indices, particularly looking for microcytic, hypochromic anemia
- Iron studies, including:
- Serum ferritin, with levels below 30 ng/mL strongly suggesting iron deficiency
- Transferrin saturation, which can be helpful in cases where ferritin may be falsely normal
- Additional tests may include a peripheral blood smear to reveal characteristic changes in red blood cell morphology, reticulocyte count to assess bone marrow response, and stool occult blood testing to screen for gastrointestinal bleeding, a common cause of iron deficiency. According to the British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults, a good response to iron therapy (Hb rise ≥10 g/L within a 2-week timeframe) in anaemic patients is highly suggestive of absolute iron deficiency, even if the results of iron studies are equivocal 1.
Clinical Considerations
- The choice of laboratory tests should be guided by clinical judgment and the suspicion of iron deficiency anemia based on patient symptoms and physical examination findings
- In cases where iron deficiency anemia is suspected but laboratory results are equivocal, a trial of iron therapy may be considered, with monitoring of hemoglobin response to guide further management.
From the Research
Diagnostic Tests for Iron Deficiency Anemia
To diagnose iron deficiency anemia, several laboratory tests can be utilized. The key tests include:
- Complete Blood Count (CBC) parameters such as red blood cell (RBC) count, hematocrit, mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC), and mean corpuscular hemoglobin (MCH) 2
- Serum ferritin levels, which is a powerful test for diagnosing iron-deficiency anemia, especially when interpreted appropriately for different patient populations 3
- Transferrin saturation, which can also be used to diagnose iron deficiency, particularly in individuals with inflammatory conditions 4
Interpretation of Test Results
The interpretation of these tests is crucial for accurate diagnosis. For instance:
- A serum ferritin level <30 ng/mL is typically indicative of iron deficiency in individuals without inflammatory conditions 4
- A transferrin saturation less than 20% can also indicate iron deficiency 4
- CBC parameters such as a hematocrit cutoff value of 35.5% can have a high discriminating power for iron deficiency anemia 2
Additional Considerations
It's important to consider the patient's clinical presentation, medical history, and risk factors when interpreting test results. For example: