Workup for Normocytic Anemia in an 85-Year-Old
Begin with a reticulocyte count to distinguish between decreased red blood cell production versus increased destruction/loss, then proceed with iron studies (ferritin, transferrin saturation), renal function (creatinine), and inflammatory markers (CRP).
Initial Laboratory Testing
The workup follows a systematic morphologic and kinetic approach 1:
Step 1: Reticulocyte Index (RI)
- Calculate the corrected reticulocyte count (reticulocyte index)
- Normal RI: 1.0-2.0
- Low RI (<1.0): Indicates decreased RBC production → proceed to evaluate for iron deficiency, vitamin B12/folate deficiency, bone marrow dysfunction, or chronic kidney disease
- High RI (>2.0): Indicates increased RBC production → evaluate for hemorrhage or hemolysis
Step 2: Iron Studies and Inflammatory Markers
- Serum ferritin
- Transferrin saturation (TSAT)
- CRP or ESR
Interpretation of iron studies 2:
- Without inflammation (normal CRP): Ferritin <30 μg/L indicates iron deficiency
- With inflammation (elevated CRP): Ferritin up to 100 μg/L may still indicate iron deficiency
- Anemia of chronic disease: Ferritin >100 μg/L with TSAT <20%
- Mixed picture: Ferritin 30-100 μg/L suggests combined iron deficiency and chronic disease
Step 3: Renal Function
- Serum creatinine and calculate creatinine clearance 3, 4
- Chronic kidney disease is a common cause of normocytic anemia in elderly patients
- Anemia can develop when creatinine ≥2.0 mg/dL, though may occur earlier in those with reduced muscle mass
Extended Workup Based on Initial Results
If reticulocyte count is low:
- Vitamin B12 and folate levels 2
- Peripheral blood smear review 1
- Consider bone marrow evaluation if diagnosis remains unclear after basic workup
If reticulocyte count is high:
- Haptoglobin, lactate dehydrogenase (LDH), indirect bilirubin for hemolysis 2
- Stool guaiac for occult blood loss 1, 3
Additional testing to consider:
Common Causes in 85-Year-Olds
The most frequent etiologies in this age group 5, 6:
- Nutritional deficiencies (45% of cases) - particularly iron, B12, folate
- Anemia of chronic inflammation (40% of cases) - from chronic diseases, malignancy
- Chronic kidney disease - increasingly common with age
- Unexplained anemia (8-17% of cases) - even after thorough evaluation
Critical Pitfalls to Avoid
Do not assume anemia is "normal aging" - anemia in elderly patients warrants full evaluation as it significantly impacts mortality, cognition, mobility, and quality of life 5, 6.
Do not overlook occult GI bleeding - particularly important when iron deficiency is identified without obvious source 3, 4. Consider colonoscopy and upper endoscopy.
Do not miss multifactorial anemia - 20% of elderly patients have more than one contributing cause 6. Address all identified deficiencies.
Watch for medication-related causes - review medications that may cause hemolysis or bone marrow suppression.
When to Refer to Hematology
Consider hematology consultation if 2:
- Cause remains unclear after extended workup
- Multiple cytopenias present (suggests bone marrow disorder)
- Concern for myelodysplastic syndrome or hematologic malignancy
- Hemolysis confirmed but etiology uncertain
The diagnostic yield improves significantly when hemoglobin drops >20% below normal range, but evaluation should not be delayed based on severity alone 7.