From the Guidelines
To evaluate iron deficiency, I recommend ordering a complete blood count (CBC), serum ferritin, iron studies (serum iron, total iron binding capacity, and transferrin saturation), and reticulocyte count, as these tests collectively provide a comprehensive assessment of iron status, allowing for accurate diagnosis and appropriate treatment planning for iron deficiency.
Key Tests for Iron Deficiency
- Complete Blood Count (CBC): helps assess hemoglobin levels, mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH) to identify microcytic, hypochromic anemia.
- Serum Ferritin: the most sensitive test for iron deficiency, with levels below 30 ng/mL strongly suggesting depleted iron stores 1.
- Iron Studies: include serum iron, total iron binding capacity, and transferrin saturation, which typically show decreased serum iron, increased total iron binding capacity, and transferrin saturation less than 16% in iron deficiency.
- Reticulocyte Count: helps assess bone marrow response.
Additional Tests
In certain cases, additional tests may be warranted:
- Soluble Transferrin Receptor Levels: increase with iron deficiency and are not affected by inflammation.
- Hemoglobin Electrophoresis: to rule out thalassemia.
- C-reactive Protein or Erythrocyte Sedimentation Rate: to assess for inflammation that can mask iron deficiency through falsely elevated ferritin.
Diagnosis and Treatment
The diagnosis of iron deficiency depends on the level of inflammation, and serum ferritin levels can be used to confirm iron deficiency, with levels below 30 ng/mL indicating depleted iron stores 1. Treatment of iron deficiency anemia with intravenous iron has been shown to be effective, with a faster response and better tolerance compared to oral iron 2.
Recent Guidelines
Recent guidelines from the British Society of Gastroenterology recommend confirming iron deficiency with iron studies prior to investigation, and using serum ferritin as the single most useful marker of iron deficiency anemia 1. The European Crohn's and Colitis Organization (ECCO) guidelines also recommend using intravenous iron as first-line treatment in patients with clinically active IBD, with previous intolerance to oral iron, with hemoglobin below 100 g/L, and in patients who need erythropoiesis-stimulating agents 2.
From the Research
Recommended Iron Deficiency Labs
The following labs are recommended for diagnosing iron deficiency:
- Complete Blood Count (CBC) parameters, such as: + Red Blood Cell (RBC) count + Hematocrit levels + Mean Corpuscular Volume (MCV) + Mean Corpuscular Hemoglobin Concentration (MCHC) + Mean Corpuscular Hemoglobin (MCH) 3
- Reticulocyte Hemoglobin Content (CHr) for diagnosis of iron deficiency, iron deficiency anemia, and monitoring of iron therapy 4
- Serum ferritin, which is considered the gold standard for diagnosing iron deficiency, but may not be accessible in resource-limited settings 3
Diagnostic Capabilities
The diagnostic capabilities of these labs are as follows:
- CBC parameters have a moderate to high discriminating power for iron deficiency anemia, with an area under the ROC curve (AUC) ranging from 0.73 to 0.96 3
- CHr has a moderate sensitivity and specificity for diagnosing iron deficiency and is less affected by inflammation than other biomarkers 4
- Serum ferritin is considered the gold standard for diagnosing iron deficiency, but may be affected by inflammation and other conditions 3, 4