Detecting iron deficiency in anemic patients with concomitant medical problems

OBJECTIVE: To determine the sensitivity and specificity of mean corpuscular volume, transferrin saturation, total iron-binding capacity, and ferritin level in determining iron deficiency in a population of anemic veterans with a wide variety of general medical diagnoses. DESIGN: Retrospective chart review. SETTING: Hospitals of the Department of Veterans Affairs in Madison and Milwaukee, Wisconsin. PARTICIPANTS: One hundred one anemic veterans with any medical condition who underwent bone marrow aspiration and serum iron studies. MEASUREMENTS AND MAIN RESULTS: Using the presence or absence of bone marrow hemosiderin as the reference standard, the sensitivity and specificity of the following serum iron indicators were calculated: mean corpuscular volume, transferrin saturation, total iron-binding capacity, and ferritin level. Of these patients, 41 (40.6%) were categorized as iron deficient, with no stainable bone marrow hemosiderin. A serum ferritin level less than or equal to 100 mu g/L provided the best sensitivity (64.9%) and specificity (96.1%) for evaluating iron stores in this patient population. When performed within 24 hours of bone marrow examination, a serum ferritin level less than or equal to 100 mu g/L was 100% accurate in separating iron-deficient from iron-sufficient patients. None of the other serum iron indicators alone or in combination performed better than ferritin level alone. CONCLUSIONS: In a population of anemic veterans with a wide variety of concomitant medical problems, a serum ferritin level less than or equal to 100 mu g/L was optimal for determining iron deficiency. This is higher than the ferritin level of less than or equal to 50 mu g/L cited in standard textbooks as evidence of iron deficiency in patients with inflammation, infection, or malignancy.