Quality specifications for reference methods.

Reference methods are a key element to the objective of traceability in laboratory medicine. However, to serve this purpose adequately, minimum analytical quality specifications are required. Here, possible strategies for deriving such specifications are presented, being based on concepts developed before by a European Working Group. Distinction is made between "genuine requirements" for reference methods (direct calibration with primary reference materials; absence of sample-related effects) and "performance specifications" (limits for random, systematic and total error, the latter in association with the number of measurements). While the former requirements are considered as conditio sine-qua-non, the latter specifications should be variable, which means that they should be tailored to the specific application of the methods. In general, it is advocated to derive performance specifications for reference methods from desirable specifications of routine methods (analyte-related), although other models should not be ruled out beforehand. Further, it is recommended that reference laboratories make special efforts to demonstrate and maintain a uniform level of quality of reference methods.