lliM Ferritin Cutoff Value Altered

In a recent Letter tathe Editor (Clin. Chem. 27:505, 1981) we evaluated a new Ferritin Radioimmunoassay kit from Diagnostic Products Corp., Los Angeles, CA. In that letter we stated that a serum ferritin cutoff of 20 g/L appeared to separate normal values from those measured in iron-deficiency anemia. The manufacturer has recalibrated the standards in the assay, resulting in a shift in the generated data. We now have re-assayed our iron-deficientanemia patients’ samples and would recommend that the previous cut-off of 20 sg/L to be reduced to 10 sg/L. Values between 10 and 20 .tg/L should be considered in a gray zone and followed-up with hematological testing. The shift in ferritin values in the healthy subjects does not appear to be of clinical significance.