From the Guidelines
To diagnose iron deficiency, serum ferritin is the single most useful marker, and levels below 30 ng/mL strongly suggest iron deficiency, as supported by the British Society of Gastroenterology guidelines 1. The diagnosis of iron deficiency involves several laboratory tests, including:
- Complete blood count (CBC) to reveal microcytic, hypochromic anemia with decreased hemoglobin, hematocrit, and mean corpuscular volume (MCV)
- Serum ferritin, which is the most sensitive test for iron stores
- Serum iron, typically decreased in iron deficiency
- Total iron-binding capacity (TIBC), usually increased in iron deficiency
- Transferrin saturation, calculated as serum iron divided by TIBC, usually below 16% in iron deficiency
- Soluble transferrin receptor levels, which increase as iron stores become depleted and can help distinguish iron deficiency from other causes of anemia These tests work together to assess iron status because iron plays a crucial role in hemoglobin production and oxygen transport throughout the body, and deficiency progresses through stages of depleted stores before affecting red blood cell production. According to the guidelines, a good response to iron therapy, defined as a hemoglobin rise of ≥10 g/L within a 2-week timeframe, is highly suggestive of absolute iron deficiency, even if the results of iron studies are equivocal 1. It's also important to note that ferritin levels must exceed 30 mg/L to achieve a 92% sensitivity for exclusion of absolute iron deficiency, as stated in the NATA guidelines 1. In some cases, a bone marrow examination with iron staining may be performed, though this is rarely necessary with modern blood tests. Overall, the combination of these laboratory tests helps to accurately diagnose iron deficiency and guide appropriate treatment.
From the Research
Labs for Iron Deficiency Diagnosis
The following labs are used to determine iron deficiency:
- Serum ferritin: measures the amount of iron stored in the body, with low levels indicating iron deficiency 2, 3, 4, 5, 6
- Transferrin saturation (TSAT): measures the percentage of transferrin that is saturated with iron, with low levels indicating iron deficiency 2, 3, 4, 5, 6
- Serum iron: measures the amount of iron in the blood, with low levels indicating iron deficiency 2, 3, 4, 6
- Total iron-binding capacity (TIBC): measures the amount of transferrin available to bind to iron, with high levels indicating iron deficiency 2, 3, 4
Additional Tests
Other tests that may be used to assess iron status include:
- Reticulocyte hemoglobin content: measures the amount of hemoglobin in reticulocytes, which can indicate iron deficiency 5
- Percentage of hypochromic red cells: measures the percentage of red blood cells that are pale and contain less hemoglobin than normal, which can indicate iron deficiency 5
- Soluble transferrin receptor: measures the amount of transferrin receptor in the blood, which can indicate iron deficiency 5
- Hepcidin: a hepatic polypeptide that plays a role in iron mobilization, which can be used to assess iron status 5