What is the most appropriate next step for an otherwise healthy 85‑year‑old woman with microcytic anemia (hematocrit 30% and mean corpuscular volume 45 fL)?

Immediate Gastrointestinal Investigation is Required

This 85-year-old woman with severe microcytic anemia (MCV 45 fL, hematocrit 30%) requires urgent upper endoscopy with duodenal biopsies and colonoscopy to identify the source of iron loss, as gastrointestinal malignancy is a critical concern in this age group. 1, 2

Why Investigation Cannot Be Deferred

• Age and anemia severity mandate investigation regardless of symptoms. The British Society of Gastroenterology guidelines explicitly state that the risks and benefits of endoscopic investigation must be weighed in elderly patients with major comorbidities, but this patient has "no serious health problems," removing the primary contraindication to investigation. 1

• The combination of severe microcytosis (MCV 45 fL) and moderate anemia (Hct 30%) indicates chronic, significant iron deficiency that demands explanation. In elderly patients, gastrointestinal blood loss—particularly from malignancy—is the most common cause, and the prevalence of dual unrelated pathology strengthens the case for imaging both upper and lower GI tracts. 1, 2

• Asymptomatic presentation does not reduce cancer risk. Iron deficiency anemia in older adults is presumed to be caused by blood loss until proven otherwise, and the possibility of gastrointestinal malignancy must be considered even without overt symptoms. 3, 2

Diagnostic Workup Algorithm

First-Line Laboratory Confirmation

• Confirm iron deficiency with serum ferritin and transferrin saturation. Ferritin <45 μg/L has optimal sensitivity and specificity for iron deficiency in practice, though ferritin may be falsely elevated by inflammation, malignancy, or hepatic disease in the elderly. 1, 2

• Add transferrin saturation if ferritin appears normal or borderline. TSAT <16-20% confirms iron deficiency even when ferritin is elevated by concurrent inflammation. 2

• Screen for celiac disease with serology before endoscopy, as it accounts for 3-5% of iron deficiency anemia cases. 1

Endoscopic Evaluation (The Correct Answer is Option E, but Both Upper and Lower GI Evaluation Are Needed)

Upper endoscopy with duodenal biopsies:

• Identifies underlying pathology in 30-50% of elderly patients with iron deficiency anemia 2
• Duodenal biopsies are mandatory to exclude celiac disease (present in 2-3% of cases) 1, 2
• Evaluates for gastric malignancy, NSAID-induced gastropathy, peptic ulcer disease, and angiodysplasia 2

Colonoscopy (or CT colonography as alternative):

• Particularly high-yield in older adults for detecting colonic carcinoma, adenomatous polyps, and angiodysplasia 1, 2
• CT colonography may be more attractive for frail elderly patients, though this patient has no serious health problems 1

Why Other Options Are Incorrect

Option A (No investigation due to age/absence of symptoms): Directly contradicts guidelines. The British Society of Gastroenterology states that evaluation should be considered in elderly patients with confirmed iron deficiency anemia, and this patient's lack of major comorbidities removes the primary reason to defer investigation. 1

Option B (Three months of iron therapy and reassessment): Dangerous approach that delays cancer diagnosis. While iron therapy should be initiated, it must occur concurrently with investigation, not as a substitute for it. 2

Option C (Investigation for multiple myeloma): Wrong diagnosis. Multiple myeloma typically causes normocytic or macrocytic anemia, not severe microcytic anemia with MCV 45 fL. This MCV indicates iron deficiency or thalassemia, not plasma cell dyscrasia. 4, 3

Option D (Referral to hematologist): Premature. Hematology consultation is appropriate for complex anemia situations or difficulty accessing IV iron, but the initial workup for microcytic anemia in an elderly patient belongs in gastroenterology to identify the bleeding source. 1

Critical Pitfalls to Avoid

• Do not attribute iron deficiency in elderly patients to dietary insufficiency alone. Mandatory GI evaluation is essential to exclude malignancy. 2

• Do not assume all microcytic anemia is iron deficiency. If iron studies are normal, consider hemoglobin electrophoresis to exclude thalassemia trait, particularly given the extreme microcytosis (MCV 45 fL). 1, 2

• Do not overlook combined deficiencies. Iron deficiency can coexist with vitamin B12 or folate deficiency; an elevated RDW suggests this possibility. 1, 2

• Do not delay investigation while awaiting response to iron therapy. The hemoglobin should rise ≥10 g/L within 2 weeks if iron deficiency is the sole cause, but investigation must proceed regardless of therapeutic response. 2

Concurrent Iron Replacement

• Start oral iron supplementation immediately (ferrous sulfate 200 mg three times daily) while diagnostic workup proceeds. 2

• Monitor hemoglobin at 2 weeks to confirm response (expected rise ≥10 g/L), which validates the iron deficiency diagnosis. 2

• Continue iron for at least 3 months after anemia correction to replenish iron stores. 2