Is the anemia related to the underlying condition?

Anemia Workup: Is This Related to the Underlying Condition?

This anemia is NOT related to the underlying condition—this is iron deficiency anemia requiring urgent gastrointestinal evaluation to identify the source of blood loss, regardless of the patient's other medical problems. 1

Laboratory Interpretation

Your patient meets diagnostic criteria for iron deficiency anemia:

• Hemoglobin 10.4 g/dL confirms anemia (below normal range for both men and women) 1
• Ferritin 30.6 ng/mL confirms iron deficiency (below the 45 ng/mL threshold that optimally balances sensitivity and specificity) 1
• MCV 96.7 fL is normocytic, which does NOT exclude iron deficiency—microcytosis may be absent in combined deficiencies or early iron deficiency 1
• Transferrin saturation 21.6% (calculated as serum iron 55 ÷ TIBC 255 × 100) is low, further supporting iron deficiency 1

The normal MCV is a critical pitfall here—many clinicians incorrectly assume iron deficiency must be microcytic, but this patient clearly has iron deficiency despite normocytic indices. 1

Why This Is NOT Anemia of Chronic Disease

While the underlying condition could theoretically cause anemia of chronic disease, several features argue strongly against this:

• Ferritin 30.6 ng/mL is too low for anemia of chronic disease, which typically shows ferritin >100 ng/mL even with concurrent iron deficiency 1
• Low transferrin saturation points to true iron deficiency rather than functional iron deficiency from inflammation 1
• The pattern demands investigation for gastrointestinal blood loss regardless of other diagnoses 1

Mandatory Next Steps

All patients with confirmed iron deficiency anemia require gastrointestinal evaluation to exclude malignancy, regardless of whether stool guaiac is negative: 1

1. Screen for celiac disease with tissue transglutaminase antibodies (IgA) and total IgA level 1

2. Perform bidirectional endoscopy (both upper endoscopy and colonoscopy): 1

   • Upper endoscopy with duodenal biopsies to evaluate for celiac disease, gastric cancer, peptic ulcer disease, or angiodysplasia 2
   • Colonoscopy (preferred over CT colonography) to exclude colorectal cancer and polyps 1, 2

3. Test for H. pylori non-invasively (stool antigen or urea breath test) 1

The negative stool guaiac does NOT eliminate the need for endoscopy—fecal occult blood testing has no role in the investigation of iron deficiency anemia due to poor sensitivity. 1

Treatment Protocol

Start oral iron replacement immediately while pursuing diagnostic workup: 2, 3

• Ferrous sulfate 324 mg (65 mg elemental iron) three times daily on an empty stomach 2, 3
• Add vitamin C 500 mg with each iron dose to enhance absorption 2
• Continue for 3 months after hemoglobin normalizes to replenish body stores 2, 4

Recheck CBC in 3-4 weeks—expect hemoglobin rise ≥2 g/dL (or ≥10 g/L within 2 weeks), which confirms iron deficiency even if initial iron studies were equivocal. 1, 2

Critical Pitfalls to Avoid

• Do not attribute this anemia to the underlying condition without completing GI evaluation—this is the most common error and can miss life-threatening malignancies 1
• Do not rely on negative stool guaiac—it is unreliable for detecting GI blood loss in iron deficiency anemia 1
• Do not assume normocytic indices exclude iron deficiency—MCV may be normal in early or combined deficiencies 1
• Explicitly ask about NSAID use (including over-the-counter ibuprofen, naproxen, aspirin)—this is commonly unreported and a frequent cause of GI blood loss 2