In a 69-year-old woman with elevated D-dimer, anemia, low hematocrit, microcytic hypochromic red cells, and high red cell distribution width, what is the appropriate workup and management?

Workup and Management of Microcytic Hypochromic Anemia with Elevated D-dimer in a 69-Year-Old Woman

This patient requires immediate evaluation for iron deficiency anemia with gastrointestinal investigation as the priority, while the elevated D-dimer should be interpreted cautiously as it is likely secondary to anemia, inflammation, or age rather than indicating acute thromboembolism in the absence of specific VTE symptoms.

Initial Diagnostic Approach

Iron Studies Are Essential First

The microcytic (MCV 75.9), hypochromic (MCH 20.7, MCHC 27.3) anemia with elevated RDW (20.6) strongly suggests iron deficiency anemia 1. Order serum ferritin immediately—if <15 μg/L, this confirms iron deficiency with 99% specificity; if <45 μg/L, iron deficiency is highly likely even with concurrent inflammation 1. If ferritin is 15-45 μg/L or if inflammatory conditions are present, add transferrin saturation to confirm 2, 1.

Critical Pitfall to Avoid

Do not assume all microcytic anemia is iron deficiency. If iron studies show normal or elevated ferritin with high transferrin saturation, order hemoglobin electrophoresis to exclude thalassemia, particularly given the disproportionately low MCV relative to anemia severity 1. In patients over 65 with iron-refractory microcytic anemia and discordant iron indices (showing iron loading rather than deficiency), consider bone marrow examination with Perls staining to identify ring sideroblasts 3.

Interpreting the Elevated D-dimer

D-dimer Context in This Patient

The D-dimer elevation (1.35) is non-specific and commonly elevated in elderly patients, anemia, inflammatory states, and malignancy—not just VTE 4. In a 69-year-old woman without acute chest pain, dyspnea, leg swelling, or hemodynamic instability, this level does not mandate immediate VTE imaging 4.

Only pursue VTE workup if she develops specific symptoms: acute dyspnea, pleuritic chest pain, unilateral leg swelling, or hemodynamic instability 4, 5. The D-dimer in this context is more likely a marker of underlying pathology causing the anemia rather than thrombosis itself.

Gastrointestinal Evaluation

When to Investigate

Any degree of iron deficiency anemia in a 69-year-old woman warrants gastrointestinal investigation, as the likelihood of serious GI pathology (including colorectal cancer) increases with age and severity of anemia 1. With hemoglobin 9.7 g/dL, this patient meets criteria for investigation.

Specific GI Workup Algorithm

1. Bidirectional endoscopy (upper endoscopy and colonoscopy) is the standard initial approach 2, 1
2. Test for Helicobacter pylori and treat if positive, as this impairs iron absorption 2
3. Obtain celiac serology (tissue transglutaminase antibodies) as celiac disease causes malabsorption 2
4. If initial endoscopy is negative and anemia persists, consider video capsule endoscopy or deep enteroscopy to evaluate for small bowel angioectasias, which are common in elderly patients and cause occult bleeding 2

Iron Repletion Strategy

Oral vs. Intravenous Iron

Start with oral ferrous sulfate (or ferrous fumarate/gluconate) 100-200 mg elemental iron daily, taken on an empty stomach or with vitamin C 500 mg to enhance absorption 2. However, given the severity of anemia (Hgb 9.7) and patient age, consider intravenous iron as first-line therapy if oral iron is not tolerated or if rapid repletion is needed 2.

Monitoring Response

Recheck complete blood count and ferritin in 4-6 weeks. If hemoglobin fails to rise by at least 1 g/dL or ferritin remains low, switch to IV iron or investigate for ongoing blood loss or malabsorption 2.

Additional Considerations

The Elevated RDW

The markedly elevated RDW (20.6) indicates significant red cell size variability, typical of iron deficiency but also seen when multiple processes coexist 6, 7. This heterogeneous microcytic pattern (elevated RDW with low MCV) strongly supports iron deficiency over thalassemia trait, which typically shows homogeneous microcytosis (normal RDW) 6, 7.

Age-Specific Concerns

In a 69-year-old woman, malignancy (particularly GI cancer) is a critical consideration. The combination of iron deficiency anemia and elevated D-dimer can occur with occult malignancy 4. Ensure thorough GI evaluation and consider age-appropriate cancer screening if not up to date.

When to Involve Specialists

• Gastroenterology: For endoscopic evaluation and management of GI bleeding sources
• Hematology: If anemia is refractory to iron therapy, if iron studies suggest iron loading rather than deficiency, or if alternative diagnoses (myelodysplasia, sideroblastic anemia) are suspected 2, 3