Establishment of reference intervals of laboratory tests using hospital patient data

Abstract

Objective: In this study, hospital patient data was used to derive reference intervals for selected clinical laboratory tests. Methods: Data were obtained indirectly using our hospital database including both sexes. No selection criteria have been applied. The data has been partitioned into only three age groups as, 3-20, 21-60 and 61 to older in order to prevent age related grouping in the distribution. The distributions have been checked by normality analysis using Kolmogorov-Smirnov test. Nonparametric percentile estimate method was used to obtain reference intervals in the age groups of 21-60 and 61 to older. In age group 3- 20, the number of data were below 120 in most tests so, GraphROC for Windows, a statistical package which performs a robust modified nonparametric method, was used to find reference intervals. Results: Most of the test data did not show Gaussian distribution form and parametric analysis of these data has failed. Instead, nonparametric analysis has succeeded in establishing the intervals in three age groups. Conclusion: The results resembled the characteristics of our hospital patient population. Especially, protein and lipid parameters showed clear differences in our population, compared to the reference values of the manufacturer, which are currently used. This study has been a clear evidence indicating the importance of determination of reference intervals and the analysis of indirectly selected hospital patient data using nonparametric statistical techniques.