Clinical utility of serum tests for iron deficiency in hospitalized patients

Serum iron and ferritin measurements lack the requisite sensitivity and/or specificity to accurately diagnose iron deficiency. To determine their utility in hospitalized patients, the authors compared the results of these tests with the presence of stainable iron in bone marrow aspirates of 301 patients. Forty (13.3%) had absent marrow iron. The serum diagnosis of iron deficiency was accepted on the basis of the following: iron less than 11 mumol/L, total iron-binding capacity (TIBC) greater than 45 mumol/L, transferrin saturation (%Sat) less than 0.20, and ferritin less than 13 micrograms/L for females and less than 25 micrograms/L for males. Using these criteria, iron deficiency was correctly diagnosed by serum iron in 41%, TIBC in 84%, %Sat in 50%, and ferritin in 90% of the patients. The serum ferritin is clearly the only useful serum test for diagnosing iron deficiency in hospitalized patients but is limited by a low sensitivity. The bone marrow examination is the most sensitive test for diagnosing iron deficiency in hospitalized patients.