Calibration of the Amersham Ferritin RIA kit using the WHO human liver ferritin international standard 80/602.

A commercial ferritin kit (Amersham Ferritin RIA (A)) was calibrated using the WHO human liver ferritin international standard 80/602 (W). The reconstituted WHO freeze-dried standard was diluted to obtain five concentration levels ranging from 10-800 micrograms/l. Logarithmic transformation of the values was performed in order to stabilize the variance, yielding the regression equation: logA = 0.0235 + 1.0022 logW. The slope of the regression line (being very close to, and not significantly different from, one) was set to one, and the relation between the untransformed values then became a proportionality: A = 1.067 x W. A WHO standard ferritin value of 15 micrograms/l (often used as cut-off value for absent iron reserves) and of 30 mu/l (often used as threshold value for the presence of stainable marrow haemosiderin iron) yielded calculated Amersham Ferritin RIA values of 16.0 micrograms/l and 32.0 micrograms/l.