Third International Reference Preparation of cardiolipin with special reference to its use in improved serological tests for treponematoses.

The Third International Reference Preparation of Cardiolipin was produced (in a quantity of 2400 ml) at the WHO Serological Reference Centre, Copenhagen, and assayed in 1957 against the Second International Reference Preparation by four laboratories in three countries. Complement-fixation and slide flocculation tests were used. The new preparation was found acceptable, and its establishment was authorized by the WHO Expert Committee on Biological Standardization.The average log(10) titres and results of analyses of variances are shown. The variances were of the usual order of magnitude, and the differences in titre between antigens containing the Second and the Third International Reference Preparations varied from -0.004 to 0.059; only two of the differences exceeded the 5% limit of significance.The use of the Third International Reference Preparation in tests for the acceptability of any new cardiolipin preparation is described.