Test Repetition From the Viewpoint of Biological Variation

Purpose: The present study was set out to investigate the effect of test repetition within the biological variation perspective by addressing reanalyzing an individual sample on total variation. This study also demonstrated to what extent a laboratory result of an individual reflects a homeostatic set-point. Methods: The total variation values were determined for different coefficients of analytical variation (CVA) corresponding optimum (CVA = 0.25 x CVI), desirable (CVA = 0.5 x CVI), and minimum (CVA = 0.25 x CVI) limits of performance specifications for imprecision. The effect of a number of analytical measurements on the total variation for a single sample was simulated. Furthermore, the percentage of closeness to the true homeostatic setting point (D) was determined for commonly used 27 analytes. Results: This study showed that the total variation reduction with reanalysis of an individual sample was lower than 19%, 10%, and 3% for the tests meeting the minimum, desirable and optimum level of specification limits, respectively. Furthermore, the reduction was only 9.4%, 5.1%, and 1.5% for duplicate analysis of an individual sample at the abovementioned limits. Conclusion: This study demonstrated that test repetition has a negligible effect on the total variation, especially when analytical performance meets optimum and desirable performance specifications. D values reported in this study can guide laboratory professionals and clinicians about to what extent a result of an individual reflects homeostatic set-point.