Establishing age/sex related serum creatinine reference intervals from hospital laboratory data based on different statistical methods

BackgroundThis is a retrospective study on a large hospital database to establish age- and sex-related mean values and reference ranges for serum creatinine (Scr), obtained with an IDMS-traceable, enzymatic method, in a Caucasian population.MethodsThe database was filtered for unique entries to reduce the presence of correlated and pathological data. Three different statistical methods, a non-parametric method, the Bhattacharya procedure and a non-linear fit of the cumulative Gaussian distribution were used to estimate the serum creatinine–age dependency for men and women, from birth till 100 years of age.ResultsScr increases with age, equal for boys and girls, up to 14 years and with a much steeper slope for boys than for girls between 14 and 20 years. We show that the Scr–age pattern is constant between 20 and 70 years with a mean of 0.90 mg/dL [0.63–1.16 mg/dL] for men and 0.70 mg/dL [0.48–0.93 mg/dL] for women. Above 70, Scr starts to slowly increase again.ConclusionsIndirect methods confirm the available reference intervals from healthy-volunteer studies and add information on age-periods not covered by these studies. As such, indirect methods can be used complementary to healthy-volunteer studies.