A European Quality Control Programme as a cooperative tool between users and a diagnostic company.

Achievement of appropriate precision is a major challenge for the clinical laboratory, particularly in specialized fields such as enzymology and immunochemistry. Especially in immunochemistry, where accuracy can only poorly be checked because of a lack of reference methods and a multitude of detectable epitopes, precision remains an important index of quality. In immunochemical methods there are three main sources of variation: differences in methodology, lot-to-lot variation and performance of the assay, the latter including the skill of the technicians and instrument performance. The results of a European Quality Control Programme for the users of one type of automated immunoassay analyser were compared with a similar Italian Quality Control Programme for users of different immunometric techniques. The precisions (%CV) of the two programmes were compared, as well as the number of values lying within one half of the biological variation of the analysed serum components. Feedback between users and manufacturers leads to a clear improvement in analysis performance, so that most of the considered values come to lie within the acceptable limits of 1/2 of the biological variation. It is concluded that both national and international quality control programmes are very useful for indicating the intrinsic quality of the quantities used in the clinical laboratory.