Quality specifications in laboratory medicine - current consensus views

Every analytical method used in laboratory medicine can be fully described in terms of its performance characteristics. Ideally, quality specifications should be available for all of these, particularly precision and bias. Specifications for these can be set using a variety of strategies. Consideration of the clinical settings of monitoring individual patients and diagnosis using reference intervals shows that generally applicable quality specifications can be based on the components of biological variation, namely, within-subject [CVI] and between-subject [CVG] variation. Current consensus is that precision should be < 1/2CV(I) and bias should be <1/4 [CVI2 + CVG2](1/2). This strategy has advantages in that data on components of biological variation are easily available on more than 180 quantities. Dissemination of information on application of objective quality specifications needs attention from those involved in publication, manufacturers and organisers of external quality assessment schemes.