Proper Workup for Anemia
The proper workup for anemia should include complete blood count (CBC), serum ferritin, transferrin saturation, total iron-binding capacity (TIBC), total serum iron, serum vitamin B12, and serum folate. 1 This comprehensive panel allows for accurate diagnosis of the underlying cause of anemia and guides appropriate treatment decisions.
Initial Laboratory Assessment
Complete Blood Count (CBC): Essential first test that includes:
- Hemoglobin concentration (preferred over hematocrit)
- Red cell indices (MCV, MCH, MCHC)
- White blood cell count with differential
- Platelet count
Reticulocyte Count: Helps distinguish between production defects and increased destruction/loss
- Low count suggests decreased production
- High count suggests blood loss or hemolysis
Iron Studies:
- Serum ferritin: Primary marker for tissue iron stores
- Transferrin saturation: Reflects iron immediately available for hemoglobin synthesis
- Total iron-binding capacity (TIBC): Helps distinguish iron deficiency from anemia of chronic disease
- Total serum iron: Completes the iron profile assessment
Vitamin Deficiency Markers:
- Serum vitamin B12: Essential for detecting macrocytic anemia due to B12 deficiency
- Serum folate: Important for identifying folate-deficient megaloblastic anemia
Interpretation of Results
Iron Status Assessment
| Parameter | Iron Deficiency Anemia | Anemia of Chronic Disease |
|---|---|---|
| MCV | Low (microcytic) | Normal |
| Serum iron | Low | Low |
| TIBC | High | Low/Normal |
| Ferritin | < 30 μg/L | > 100 μg/L |
| Transferrin saturation | < 15% | < 20% |
Vitamin Deficiency Assessment
- B12 deficiency: Macrocytic anemia (high MCV), normal iron studies
- Folate deficiency: Macrocytic anemia (high MCV), normal iron studies
Clinical Considerations
Serum ferritin is the most powerful test for iron deficiency, with levels <15 μg/L highly specific for iron deficiency and <45 μg/L considered the optimal cutoff in clinical practice 1
In patients with inflammatory conditions, ferritin may be falsely elevated as an acute phase reactant, making transferrin saturation more valuable in these cases 2
For patients with chronic kidney disease, the KDIGO guidelines specifically recommend this complete panel for initial evaluation of anemia 3
The reticulocyte hemoglobin content can provide additional information about iron availability for erythropoiesis, especially in complex cases 4
Common Pitfalls to Avoid
Relying solely on hemoglobin: An isolated hemoglobin measurement has both low specificity and sensitivity for determining the cause of anemia 5
Overlooking inflammation: Inflammatory states can mask iron deficiency by elevating ferritin levels while iron stores remain low 2
Incomplete testing: Failing to measure both iron parameters and vitamin levels can lead to missed diagnoses, especially in cases of mixed deficiencies
Misinterpreting ferritin: In chronic kidney disease or inflammatory states, higher ferritin cutoffs (>100-500 ng/mL) may still be consistent with iron deficiency 3
This comprehensive approach to anemia workup ensures proper identification of the underlying cause and facilitates appropriate treatment decisions, ultimately improving patient outcomes by addressing the specific deficiency or disorder responsible for the anemia.