MULTICENTRIC REFERENCE VALUES - SHARED REFERENCE LIMITS

In order to obtain shared reference limits, three laboratories in the same geographical area with a homogeneous population have developed a proposal to produce multicentric reference values. The strategy simula tes a virtual laboratory, actually formed by the laboratories involved ; the reference limits produced in the virtual laboratory are in fact derived from the blend of reference values obtained by each laboratory . Each laboratory has chosen its own reference sample and has measured the biochemical quantities under study. Reference individuals (n = 17 1) and 15 biochemical quantities among the most measured in clinical l aboratories were selected. The reference values obtained in each labor atory were blended when permitted by the Harris & Boyd test (Clin Chem 1990; 36:265-70). The multicentric reference limits obtained by the v irtual laboratory for each quantity were estimated according to the re commendations of the International Federation of Clinical Chemistry. F or each quantity, each laboratory, with the results observed in their reference sample, estimated the diagnostic specificity, using as cut-o ff values the corresponding multicentric reference limits. Each observ ed value of diagnostic specificity was compared with the theoretical d iagnostic specificity value, equal to 0,975, that should be observed w hen a reference limit is used as cut-off value. The multicentric refer ence limits obtained by the virtual laboratory are valid in all cases with the exception of the upper reference limit for the concentrations of calcium(II) and urate in serum in one of the laboratories.