The use of "clear" enzyme control materials

Low turbidity, "clear" enzyme controls commercially produced in three concentrations and conventional human lyophilized control sera, which are more turbid, were evaluated to determine which was superior for quality control purposes. Criteria used to evaluate the controls were: 1) turbidity measurement, 2) daily assays for 30 days to estimate day-to-day precision, and 3) stability of the enzyme assay value for these controls when they were reconstituted and frozen for 0 to 30 days and 0 to 10 days with three aliquots separately prepared and frozen for 0 to 10 days for a total of 30 days. The controls were analyzed for lactate dehydrogenase, alanine aminotransferase, aspartate aminotransferase, creatine kinase, and alkaline phosphatase activities with the Perkin-Elmer KA 150 enzyme analyzer.