Transferability of reference values

ADDITIONAL TOPICS Transferability of Reference Values The determination of refiable reference values for each test in the laboratory s repertoire is a major task and is often far beyond the capabilities of the individual laboratory. It would therefore be convenient if reference values generated in another laboratory could be used. This is especially important when ethical considerations limit the number of available individuals (e.g., when producing pediatric reference values). Then, cooperative establishment of reference values may be necessary. 

A major prerequisite for transfer of reference values is that the populations be homogeneous (i.e., there should be no major ethnic, social, or environmental differences among them). 

However, the problem of analytical transferability remains. The optimal, but usually very unrealistic, situation assumes that the analytical methods, including their calibration and quality assurance, are identical in the laboratories. A more pragmatic approach involves standardization of analytical protocols, common calibration, design of a sufficiently efficient external quality control scheme, and the use of mathematical transfer functions if the results still are not directly comparable. 

The parameters of transfer functions may be estimated from the results obtained by analysis of a sufficient number of specimens (preferably human) spanning the relevant range of concentrations in all participating laboratories. Sometimes functions obtained by simple linear regression suffice using y=Uo + iX, the constant term Uq compensates for systematic shifts among the methods, whereas the coef- 

Multicenter production of reference values is gaining acceptance, both as a theoretical concept and as a practical approach. A Spanish study introduced a cooperative model, simulating a virtual laboratory for 15 biochemical quantities. A recent project in the Nordic countries (NORIP ) was aimed at the production of common reference intervals for 25 analytes. 

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See also in sourсe #XX -- [ ]

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