Iron deficiency laboratory tests
Pro Research Analysisby 
Searched over 200M research papers
Key Laboratory Tests for Iron Deficiency Diagnosis
Several laboratory tests are used to diagnose iron deficiency, each with its own strengths and limitations. The most widely used and informative tests include serum ferritin, transferrin saturation (TSAT), serum iron, total iron-binding capacity (TIBC), red cell indices (such as mean corpuscular volume, MCV), and hemoglobin concentration. Serum ferritin is considered the most powerful single test for diagnosing iron deficiency anemia, with high diagnostic accuracy, especially when interpreted in the context of the patient’s clinical background 178. TSAT is also emphasized as a key marker, particularly in patients with chronic diseases, as it is less affected by inflammation compared to ferritin .
Stages of Iron Deficiency and Test Interpretation
Iron deficiency can be classified into three stages, and different tests are more useful at each stage. In the earliest stage (iron depletion), serum ferritin is the most sensitive marker, reflecting depleted iron stores. As iron-deficient erythropoiesis develops, TSAT, free erythrocyte protoporphyrin (FEP), and MCV become more informative. In the final stage, iron deficiency anemia, hemoglobin concentration drops below normal 378. No single test is best for all stages; instead, these tests complement each other to provide a full picture of iron status .
Red Cell Indices and Complete Blood Count
Red cell indices, such as MCV and mean corpuscular hemoglobin (MCH), along with hemoglobin and hematocrit from a complete blood count, are useful initial screening tools. These are especially helpful in children and in outpatient settings for early detection of iron deficiency anemia, as they are widely available and inexpensive 256. However, in mild cases, these indices may overlap with normal values, making diagnosis more challenging .
Advanced and Additional Laboratory Markers
Other laboratory markers, such as erythrocyte protoporphyrin (EP or ZPP), soluble transferrin receptor (sTfR), and hepcidin, can provide further information, especially in complex cases or when iron deficiency coexists with chronic disease or inflammation 69. Bone marrow iron examination remains the gold standard in difficult cases, particularly in hospitalized patients with chronic disease, malignancy, or liver disease 78.
Limitations and Variability in Laboratory Testing
It is important to recognize that laboratory tests for iron deficiency can be affected by analytic errors and biological variation. Serum iron and TIBC show higher variability, while hemoglobin and red cell indices are more stable. Ferritin and TSAT can be influenced by inflammation, infection, or liver disease, which may complicate interpretation in certain populations 1410.
Special Considerations in Chronic Disease
In patients with chronic diseases such as heart failure, chronic kidney disease, or inflammatory conditions, both ferritin and TSAT are recommended for routine surveillance. TSAT is often more reliable in these settings due to its lower sensitivity to inflammation, with a TSAT value below 20% commonly used as a diagnostic threshold 910.
Conclusion
Diagnosing iron deficiency relies on a combination of laboratory tests, with serum ferritin and TSAT being the most central. The choice and interpretation of tests should be tailored to the clinical context, the stage of deficiency, and the presence of any underlying chronic or inflammatory conditions. Using a combination of these markers allows for accurate detection and management of iron deficiency across diverse patient populations.
Sources and full results
Most relevant research papers on this topic