Analytic clinical laboratory precision. State of the art for selected enzymes

Results of precision estimates are reported for selected enzyme analytes. Laboratories that participated in regional quality control programs supplied data to a centralized data processing service (College of American Pathologists Computer Center). These data, representing several regional groups which used different commercial sources of control serum, were statistically analyzed by regression of coefficient of variation (CV) upon concentration of analyte using a modified polynomial regression technic. Tolerance limits for long-term within-laboratory precision were developed from this data. Estimated CVs were extracted at selected analyte concentrations, and tolerance limits for CVs at these concentrations were developed. In addition, selected individual methods within the larger groups were individually examined to evaluate effect of control material matrix upon clinical estimates of enzyme precision. Differences in selected method groups are discussed.