International collaborative study to evaluate and calibrate two recombinant L chain Ferritin preparations for use as a WHO International Standard

Abstract

Objectives: To evaluate and calibrate two candidate preparations for the 4th International Standard for Ferritin (Human, Recombinant) (codes: 19/118 and 19/162) against the 3rd International Standard for Ferritin (Human, Recombinant) (code: 94/572), and three serum commutability samples in an international collaborative study involving 12 laboratories in nine countries. Methods: Eleven of the 12 participating laboratories performed Ferritin quantitation using automated assay platforms and one laboratory used a manual ELISA kit. Results: There was better overall agreement between all laboratories and between assay methods for the potency of preparation 19/118 than for preparation 19/162. The overall geometric mean potency (from all methods) of the candidate 4th International Standard, 19/118, was 10.5 μg/ampoule, with inter-laboratory variability, expressed as % geometric coefficient of variation (GCV), of 4.7%. Accelerated stability studies have predicted both 19/118 and 19/162 to be very stable for long term storage at-20 °C. Conclusions: The candidate 4th International Standard for Ferritin (Human, Recombinant) (19/118) has been shown to be immunologically similar to the 3rd International Standard for Ferritin (Human, Recombinant) (94/572). It was recommended to and accepted by the WHO Expert Committee on Biological Standardization that 19/118 be established as the 4th International Standard for Ferritin (Human, Recombinant) with an assigned potency of 10.5 μg/ampoule and expanded uncertainty limits 10.2-10.8 μg/ampoule (95% confidence; k=2.23).