European specifications for imprecision and inaccuracy compared with operating specifications that assure the quality required by US CLIA proficiency-testing criteria.

Proposed and interim European quality specifications for imprecision and inaccuracy have been compared with the US CLIA total error criteria for proficiency testing (PT). To assess the relative demands of separate imprecision and inaccuracy specifications vs total error criteria, we derived the imprecision and inaccuracy that would be allowable if a testing process were to provide 90% assurance of achieving the analytical quality required by CLIA PT criteria. Charts of operating specifications (OPSpecs charts) were prepared for commonly used single-rule and multi-rule quality control procedures with 2 and 4 control measurements per run. Of the 23 tests studied, the proposed European specifications for imprecision and inaccuracy were more demanding than the CLIA requirements for 12 tests (albumin, alkaline phosphatase, amylase, calcium, chloride, creatinine, lactate dehydrogenase, lithium, magnesium, total protein, sodium, and thyroxine). The CLIA total error criteria were more demanding than the proposed European specifications for nine tests (alanine aminotransferase, aspartate aminotransferase, total bilirubin, cholesterol, creatine kinase, iron, triglycerides, uric acid, and urea nitrogen). Two tests (glucose, potassium) showed different requirements at different decision levels. Manufacturers and laboratory analysts need to compare these different quality specifications on a test-by-test basis to guide the development, selection, evaluation, and control of laboratory measurement procedures.