A study showing a high degree of interlaboratory variation in the assay of human interferon

Identical human fibroblast interferon samples were assayed in four different laboratories, in all of which the international reference standards were used. Up to tenfold differences in titer were observed between the laboratories. Differences of this magnitude make meaningful comparisons of clinical and other interferon studies difficult and clearly indicate the need for an internationally accepted standardized interferon assay system.