[Allowable limits of analytical error which can guarantee the reliability of reference intervals for interpretation...

The International Organization for Standardization (ISO) developed a guide to the expression of uncertainty in measurement (GUM). The purpose of such guidance is to provide a basis for the international comparison of measurement results. In this study, we propose a basic protocol to evaluate and express uncertainty in measurement for routine test results in the clinical laboratory. We also sought to investigate the effects of measurement errors on the evaluation of biological variations in healthy subjects. To this end, we analyzed the allowable limits of analytical error which guarantee the reliability of reference intervals for the interpretation of clinical laboratory data. As a conclusion, we suggest that 1/2 or less of biological intraindividual variations is an appropriate criterion for an allowable limit of uncertainty to be applied in health check-ups, and this value is in agreement with previous reports. If this criterion as a marker for intra laboratory imprecision is met, it suggests that a given institute is able to evaluate time series changes in follow-up of individual data. If the reference interval of laboratory data for disease screening is shared by different institutes, it is suggested that a criterion of 1/4 or less of a biological inter- pulse intra-individual variation is appropriate. This criterion appears to be the goal for analytical inter-laboratory variations.