The variability of serum ferritin and other blood iron indices

To evaluate the variability of various serum ferritin (SF) analysis techniques, four assay reagent kits and four commercial laboratories were compared both in the SF values obtained for the same six standards, and in the values used to classify a sample as "normal" or "abnormal". Analysis of the four SF reagent kits indicated considerable variability which was greatest at the lower SF concentrations. Test-retest variability was lowest in Kit 4 (Abbott) and exhibited the lowest %CV at each SF standard. Therefore, this SF kit was recommended for clinical use.;Comparison of SF results from the laboratories and the reagent kits demonstrated differences both in their SF determinations on the same sample, and in their diagnosis of "normal" values. The criteria by which a SF value was diagnosed as "normal" or "abnormal" was dependent on the method used in its determination. Therefore, a universal value cannot be used in the diagnosis of iron status otherwise erroneous results may be produced. (Abstract shortened by UMI.)...