This article is intended as a guide for the production of biological reference values of healthy people (physiological reference values) by several clinical laboratories using the same measurement system. This guide is a proposal from the Catalan Association of Clinical Laboratory Sciences to be applied worldwide at a regional level. This guide makes it possible for all clinical laboratories in a region using the same measurement system to adopt the same physiological reference limits. The model presented here is based on the assumption that the production of physiological reference values is a professional task that should be shared by both clinical laboratories and the in vitro diagnostics industry.

Nine clinical laboratories in different regions of Spain have shared the search for reference individuals and the production of reference values for urinary component-to-creatininium concentration ratios measured in first morning urine samples using RD/Hitachi analysers. These urinary quantities include albumin, calcium(II), chloride, magnesium(II), phosphate, potassium ion, protein, sodium ion, urate and urea. All the logistic work was done in co-operation with the reagents' and analysers' supplier (Roche Diagnostics España, S.L., Sant Cugat del Vallès, Catalonia, Spain). From the blend of reference values obtained by each laboratory, the multicentre reference limits were estimated parametrically after mathematical transformation of original data.