To the Editor.
—Bessman and McClure1 suggested that the RDW is a useful screening test for iron deficiency in the outpatient setting. Their earlier article in which iron and transferrin saturation were used as the "gold standard" yielded similar results.2 Their current data1 used a serum ferritin level of less than 30 μg/L as the gold standard for iron deficiency, which, as they noted, is a more appropriate though imperfect means of assessing iron deficiency.3They cited our article4 in which the RDW was found to correlate poorly with the ferritin level. They attributed the differences to the fact that we studied inpatients who were acutely ill, which, they argue, confounds the serum ferritin level. Their argument is correct in that we found that the specificity of the RDW was only 54% (a point we acknowledged in our article). However, we also reported that the
Thompson WG. Red Cell Distribution Width in Alcohol Abuse and Iron Deficiency Anemia. JAMA. 1992;267(8):1070-1071. doi:10.1001/jama.1992.03480080040013