What are the recommended initial laboratory tests for a female patient in her 60s with a Mean Corpuscular Volume (MCV) of 64 and abnormal Red Blood Cell (RBC) morphology?

Laboratory Workup for a Female Patient in Her 60s with MCV of 64 and Abnormal RBC Morphology

For a female patient in her 60s with a significantly low MCV of 64 and abnormal RBC morphology, the recommended initial laboratory tests should include iron studies, hemoglobin electrophoresis, and evaluation for chronic disease markers to diagnose the underlying cause of microcytic anemia.

Initial Laboratory Evaluation

Essential Tests:

• Complete Blood Count (CBC) with indices (already performed showing MCV of 64)
• Iron studies:
  • Serum ferritin
  • Transferrin saturation (TSAT)
  • Serum iron
  • Total iron binding capacity (TIBC)
• Reticulocyte count - to assess bone marrow response to anemia
• Hemoglobin electrophoresis - to evaluate for thalassemia
• Peripheral blood smear review - for detailed morphological assessment

Additional Tests Based on Clinical Suspicion:

• Inflammatory markers:
  • C-reactive protein (CRP)
  • Erythrocyte sedimentation rate (ESR)
• Renal function tests:
  • Blood urea nitrogen (BUN)
  • Serum creatinine
• Liver function tests
• Serum B12 and folate levels - to rule out concomitant deficiencies

Interpretation Framework

MCV of 64 (Severely Microcytic):

This extremely low MCV (normal range 80-100 fL) strongly suggests either:

1. Iron deficiency anemia (severe)
2. Thalassemia trait/disease
3. Anemia of chronic disease (less commonly this severe)

Significance of Abnormal RBC Morphology:

Different morphological findings point to specific etiologies 1:

Morphology	Possible Diagnosis
Hypochromic, microcytic cells	Iron deficiency or thalassemia
Target cells	Thalassemia, liver disease
Basophilic stippling	Thalassemia, lead poisoning
Fragmented cells	Microangiopathic hemolytic anemia
Sickle cells	Hemoglobinopathies

Diagnostic Algorithm

1. First tier: Evaluate iron status with ferritin and transferrin saturation

   • If ferritin <30 μg/L → Iron deficiency anemia 2
   • If ferritin 30-100 μg/L with TSAT <16% → Consider iron deficiency with concomitant inflammation 2
   • If ferritin >100 μg/L with TSAT <16% → Anemia of chronic disease 2

2. Second tier: If iron studies inconclusive or suggest thalassemia:

   • Proceed with hemoglobin electrophoresis
   • Assess RBC count (often elevated in thalassemia relative to hemoglobin level)
   • Evaluate RDW (typically normal in thalassemia, elevated in iron deficiency) 2

3. Third tier: If diagnosis remains unclear:

   • Consider bone marrow examination
   • Genetic testing for hemoglobinopathies or rare RBC membrane disorders 3

GI Evaluation Considerations

For confirmed iron deficiency anemia in a female patient in her 60s:

• Upper GI endoscopy with duodenal biopsies (to rule out celiac disease)
• Colonoscopy (to rule out colorectal cancer or other sources of blood loss)

This is particularly important as dual pathology occurs in 10-15% of cases 2.

Common Pitfalls to Avoid

1. Attributing iron deficiency solely to poor diet without proper GI investigation in older adults 2
2. Overlooking thalassemia in patients with microcytic anemia and normal iron studies 2
3. Failing to evaluate for other nutrient deficiencies that may coexist with iron deficiency 2
4. Inadequate follow-up after initiating treatment - hemoglobin should be monitored regularly 4

Monitoring Recommendations

• Repeat CBC in 4-6 weeks after initiating therapy
• Monitor iron studies until normalization
• Continue treatment for 3 months after hemoglobin normalizes to replenish iron stores 2

By following this systematic approach, the underlying cause of microcytic anemia with abnormal RBC morphology can be accurately identified and appropriately managed.