RefVal: a program implementing the recommendations of the International Federation of Clinical Chemistry on the statistical treatment of reference values

RefVal is a computer program that implements the recommendations of the International Federation of Clinical Chemistry on the statistical treatment of reference values. The program performs the following main tasks: graphical display of the distribution of reference values, identification or elimination of outliers, testing of the fit of the distribution to Gaussian shape (coefficients of skewness and kurtosis, Anderson-Darling's test, Cramér-von Mises' test, Kolmogorov-Smirnov's test), non-parametric and parametric estimation of reference limits (fractiles, percentiles). The parametric estimation method is based on a two-stage mathematical transformation of data: (1) Manly's exponential transformation (to remove skewness) and (2) John and Draper's modulus transformation (to adjust for remaining kurtosis). The program exists in different versions. The paper describes two of these: (1) a library of FORTRAN functions and subroutines and (2) a Pascal PC program that runs under MS-DOS.