A Comparison of Eleven Commercial Kits for the Determination of Serum Ferritin Levels

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Abstract
Eleven commercial kits for serum ferritin were compared. Seven kits used RIA (radioimmunoassay) and 4 IRMA (immunoradiometric assay) methodology. Seven kits used human liver ferritin, 2 human spleen ferritin and 2 undefined human ferritin as standard material. Incubation times varied between 30 min and 36 h. Only 4 kits gave normal ranges determined with the kit in question. All values were compared with the kit in routine use. Although correlation of results was good in 10 cases, (r = 0.903-0.993) the numerical values varied greatly, (slope of the regression line b = 0.437-1.94). These values were obtained from at least 30 sera for each kit. Seven kits gave significantly different results from the routine kit (P < 0.05-Wilcoxon matched pairs test-2 tail value). Inter and intra-assay coefficients of variation were < 12.5% in all cases within the range of interest. Four kits showed a pronounced non-linear correlation with the routine kit and one of the IRMA kits exhibited a high-dose hook effect within the standard curve. The other 3 IRMA kits showed no such effect up to 2000 .mu.g.cntdot.l-1 (under assay conditions).