COLLABORATIVE ASSAY OF EEC STANDARDS FOR BOVINE TUBERCULINS

Seven laboratories participated in a trial in guinea-pigs designed to compare the potencies of bovine tuberculins used for testing cattle in member countries of the European Economic Community. When assayed in guinea-pigs sensitized with a killed strain of Mycobacterium bovis, PPD tuberculins and old tuberculins both gave consistent results when compared separately; due to qualitative differences of these two classes of tuberculin, however, there were sometimes significant deviations from parallelism of the dose-response curves when comparing PPD and old tuberculin (OT). Assays in guinea-pigs sensitized with living strains of M. bovis resulted in wider variations in relative potency, and estimates with wider confidence limits. In guinea-pigs sensitized with the killed bovine strain, the potency of the proposed international standard for bovine PPD was almost identical to that of the EEC Standard bovine PPD weight for weight and the latter had a significantly lower potency than that of the EEC Standard OT which, in turn, was significantly lower in potency than the French reference bovine HCSM tuberculin. In guinea-pigs sensitized with living strains of M. bovis the EEC Standard for bovine PPD had a significantly higher potency than both the proposed international standard for bovine PPD and the EEC Standard for OT. In guinea-pigs sensitized with Mycobacterium avium, PPDs of bovine tuberculin had a lower potency than old tuberculins, demonstrating that the PPDs were more specific. © 1979 The International Association of Biological Standardization.