CBC Interpretation: Microcytic Anemia with Thrombocytopenia
This CBC shows microcytic hypochromic anemia (MCV 77.7 fL, MCH 23.8 pg, MCHC 30.7 g/dL, Hgb 10.5 g/dL) with elevated RDW (16.4%) and mild thrombocytopenia (102×10³/µL), most consistent with iron deficiency anemia that requires immediate serum ferritin testing and comprehensive gastrointestinal evaluation to exclude malignancy.
Key Findings
Red Blood Cell Abnormalities
- Microcytic anemia: MCV 77.7 fL (low), MCH 23.8 pg (low), MCHC 30.7 g/dL (low) with hemoglobin 10.5 g/dL indicates small, pale red cells
- Elevated RDW 16.4%: Suggests heterogeneous red cell population, characteristic of iron deficiency or combined deficiency states 1
- The combination of microcytosis with elevated RDW strongly points toward iron deficiency rather than thalassemia (which typically has normal RDW) 1
Platelet Abnormality
- Mild thrombocytopenia: 102×10³/µL is below normal range
- This combination of microcytic anemia with thrombocytopenia raises concern for chronic blood loss or bone marrow pathology
White Blood Cell Parameters
- Total leukocyte count 7.37×10³/µL is normal
- Monocyte count 0.65×10³/µL is within normal limits
Diagnostic Approach
Immediate Next Step
Order serum ferritin immediately - this is the most powerful test for iron deficiency 1. A ferritin <12 μg/dL is diagnostic of iron deficiency, though values between 12-100 μg/dL can still indicate deficiency in the presence of inflammation, malignancy, or liver disease 1.
Critical Consideration
The elevated RDW (16.4%) may indicate:
- Iron deficiency (most likely given microcytosis)
- Combined deficiency (e.g., concurrent folate or B12 deficiency) 1
- Chronic disease with iron dysregulation
Mandatory Gastrointestinal Investigation
If iron deficiency is confirmed, comprehensive GI evaluation is essential to exclude malignancy, as this is the most common cause in adults (excluding menstruating women) 1:
Upper GI endoscopy with small bowel biopsies - 30-50% diagnostic yield, and 2-3% of iron deficiency anemia patients have coeliac disease 1
Colonoscopy or barium enema - required even if upper endoscopy is positive, as dual pathology occurs in ~10% of cases 1
Do not assume dietary deficiency alone - even with positive dietary history, full GI investigation is required 1
Common Pitfalls to Avoid
- Don't assume thalassemia without testing: While microcytosis occurs in thalassemia, the elevated RDW and low hemoglobin favor iron deficiency 1
- Don't skip GI evaluation: Asymptomatic gastric and colonic carcinoma commonly present with iron deficiency anemia 1
- Don't rely on ferritin alone if elevated: Ferritin >100 μg/dL essentially excludes iron deficiency, but values 12-100 μg/dL require clinical correlation as ferritin is an acute phase reactant 1
- Don't overlook the thrombocytopenia: This adds complexity and may suggest chronic blood loss, bone marrow involvement, or concurrent pathology
Additional Testing Needed
Beyond ferritin:
- Transferrin saturation (<30% supports iron deficiency) 1
- Peripheral blood smear to evaluate red cell morphology
- Reticulocyte count to assess bone marrow response
- Consider hemoglobin electrophoresis if thalassemia is suspected based on ethnicity or family history 1
- Evaluate for occult blood loss: stool occult blood testing as part of GI workup