Changes of methodology and their potential effects on data banks for drug effects on clinical laboratory tests.

Some of the implications of method changes on data banks-for the effects of drugs on clinical laboratory tests are discussed. Using data from Wellcome Clinical Chemistry Quality Control Programmes, separated by a period of ten years, significant changes of methodology used by participants are illustrated. These changes are related to a recognised listing of drug effects in clinical chemistry tests available in 1975. It is suggested that information from external quality assessment schemes is used periodically to review the relevance of data in relation to major changes of methodology.