Ret‐Y a measure of reticulocyte size: a sensitive indicator of iron deficiency anemia

Summary In this study the size of reticulocytes was measured, reticulocyte‐Y (Ret‐Y), to distinguish iron deficiency anemia from the anemia of chronic disease using a Sysmex XE2100 cell counter. We evaluated this parameter prospectively in 100 patients seen for the evaluation of anemia. A clinical diagnosis of iron deficiency anemia or anemia of chronic disease was made on the basis of a complete blood count, examination of the peripheral smear, and serum ferritin along with a history and physical examination. We analyzed the sensitivity and specificity of the Ret‐Y in relationship to the clinical diagnosis. We also measured serum transferrin receptor levels to use as the gold standard laboratory test for iron deficiency against which we compared the Ret‐Y. In 40 normal individuals with normal serum ferritin and transferrin receptor levels the mean Ret‐Y was 1874 ± 178 (1 SD). The mean Ret‐Y in the anemia of chronic disease group (n = 62) was 1722 ± 162, not significantly different from normal. The mean Ret‐Y value among iron‐deficient patients (n = 38), was 1407 ± 136 (P