What lab work should be ordered to confirm severe anemia and check for other issues?

Laboratory Workup for Severe Anemia (Hemoglobin 6)

For a patient with severe anemia (hemoglobin 6 g/dL), a comprehensive laboratory workup should include iron studies, complete blood count with indices, reticulocyte count, and evaluation for other potential causes of anemia. 1, 2

Initial Laboratory Assessment

• Complete blood count (CBC) with red cell indices to confirm the severity of anemia and provide clues to etiology 1, 2
• Reticulocyte count to assess bone marrow response to anemia 1, 2
• Iron studies including serum ferritin, transferrin saturation (TSAT), serum iron, and total iron-binding capacity (TIBC) 1
• Serum bicarbonate to assess for metabolic acidosis, especially if chronic kidney disease is suspected 1
• C-reactive protein to evaluate for inflammation that might affect interpretation of iron studies 2

Iron Deficiency Evaluation

• Serum ferritin is the most useful single marker for iron deficiency; levels <30 μg/L confirm iron deficiency in the absence of inflammation 1
• Transferrin saturation <16% suggests iron deficiency but should be interpreted alongside ferritin 1
• In patients with inflammation, malignancy, or liver disease, ferritin may be falsely elevated; iron deficiency is unlikely if ferritin >100 μg/L 1
• Consider a trial of iron therapy if iron deficiency is suspected despite equivocal lab results; a hemoglobin rise ≥10 g/L within 2 weeks strongly suggests iron deficiency 1

Additional Testing Based on Initial Results

• If microcytic anemia (MCV <80 fL):

  • Hemoglobin electrophoresis to rule out hemoglobinopathies, especially in patients with appropriate ethnic background 1
  • Stool guaiac test to check for occult gastrointestinal bleeding 1

• If normocytic anemia (MCV 80-100 fL):

  • Kidney function tests (BUN, creatinine) to evaluate for chronic kidney disease 1
  • Vitamin B12 and folate levels to rule out deficiencies that may mask microcytosis 3, 4
  • Thyroid function tests to rule out hypothyroidism 2

• If macrocytic anemia (MCV >100 fL):

  • Vitamin B12 and folate levels 3, 4
  • Methylmalonic acid and homocysteine levels if B12 deficiency is suspected despite normal B12 levels 3
  • Liver function tests to evaluate for liver disease 2

• If hemolysis is suspected:

  • Lactate dehydrogenase (LDH), haptoglobin, and bilirubin levels 2
  • Direct antiglobulin test (Coombs test) 5

Monitoring Parameters

• For patients with chronic kidney disease (CKD):
  • Monitor hemoglobin at least every three months if GFR <30 ml/min per 1.73 m² 1
  • Check serum calcium, phosphorus, and intact parathyroid hormone (iPTH) levels 1
  • Monitor serum bicarbonate concentration at least every three months 1

Important Considerations

• The severity of anemia (hemoglobin 6 g/dL) warrants urgent evaluation and may require blood transfusion based on symptoms and hemodynamic stability 2, 6
• In men and post-menopausal women with iron deficiency anemia, gastrointestinal evaluation (upper endoscopy and colonoscopy) is recommended to rule out malignancy 1, 7
• Avoid high-dose folic acid supplementation without ruling out B12 deficiency, as it may mask B12 deficiency symptoms while allowing neurological damage to progress 4
• Consider bone marrow examination if the diagnosis remains unclear after initial testing, especially if multiple cytopenias are present 8

By following this systematic approach to laboratory evaluation, the underlying cause of severe anemia can be identified, allowing for appropriate targeted therapy to address both the anemia and its underlying etiology.