From the Guidelines
The initial workup for anemia should begin with a complete blood count (CBC) with differential, peripheral blood smear, reticulocyte count, and iron studies including serum ferritin, serum iron, total iron-binding capacity (TIBC), and transferrin saturation. Ferritin serves as the most sensitive test for iron deficiency, with levels below 30 ng/mL strongly suggesting iron deficiency anemia 1. TIBC measures the blood's capacity to bind iron with transferrin and is typically elevated (>450 μg/dL) in iron deficiency anemia. Additional baseline tests should include:
- Vitamin B12 and folate levels
- Liver function tests
- Renal function tests
- Hemolysis markers (LDH, haptoglobin, bilirubin) The mean corpuscular volume (MCV) from the CBC helps categorize anemia as microcytic, normocytic, or macrocytic, guiding further investigation. For patients over 50 or those with gastrointestinal symptoms, evaluation for occult blood loss is essential 1. This comprehensive initial approach allows for proper classification of anemia and directs subsequent targeted testing based on the suspected underlying cause, whether it's nutritional deficiency, chronic disease, hemolysis, or bone marrow dysfunction. According to the most recent guidelines, the goal ferritin is 50 ng/mL, regardless of sex at birth, and a TSAT <20% has high sensitivity for diagnosing absolute or functional iron deficiency 1.
From the Research
Initial Steps in Anemia Workup
The initial steps in the workup for anemia include:
- A thorough history and physical examination
- A complete blood cell count (CBC) to provide important clues to the classification and cause of anemia 2
- Examination of the mean corpuscular volume (MCV) to help classify the anemia
Supplemental Tests
Supplemental tests that may be included in the workup for anemia are:
- Peripheral blood smear
- Reticulocyte count to serve as a useful screen for hemolysis or blood loss 3
- Iron panel, which includes:
- Ferritin levels
- Iron levels
- Total Iron-Binding Capacity (TIBC)
- Transferrin saturation
- Levels of vitamin B12, folate, lactate dehydrogenase, haptoglobin, and bilirubin 2
Diagnostic Tests
Other diagnostic tests that may be used to evaluate anemia include:
- Hemoglobin electrophoresis to separate microcytic anemias 4
- Erythrocyte size-distribution width to distinguish iron deficiency from thalassemia minor 4
- Micro-Coombs' test and ektacytometry to evaluate hemolytic anemias 4
- Molecular testing to aid in the diagnostic process 3
- Bone marrow examination, which may be required for diagnosis in some cases 3
- Reticulocyte hemoglobin content (Ret-Hb) as a screening test for iron deficiency anemia 5
Limitations of Certain Tests
It's worth noting that serum iron and TIBC may not provide additional information in the diagnosis of iron deficiency anemia if serum ferritin is available, and these tests may be considered redundant 6