The 1978 College of American Pathologists survey of analyses of five serum enzymes by 450 laboratories.

Sets of survey specimens having known linear interralationships were analyzed on four occasions by approximately 450 laboratories for the five enzymes lactate dehydrogenase, aspartate aminotransferase, creatine kinase, alanine aminotransferase, and alkaline phosphatase. The results are summarized in terms of the apparent precision and relative accuracy of various analytical systems, and some apparent problems in enzyme assays are identified. The results show that interlaboratory differences in enzyme analyses are not due primarily to differences in the way laboratorians utilize their analytical systems but rather are due to fundamental differences in the instruments and reagents supplied to the laboratorians. The attainment of interlaboratory comparability of enzyme analyses is a problem that can best be addressed by the manufacturers of instruments and reagents, rather than by individual laboratorians.