title: Quality assurance of the analytic process: pre- and postanalytic variation.
abstract: This article attempts to define and identify sources of variation in laboratory analysis that occur predominantly "away" from the analytic bench. Problems in the derivation and application of reference ranges are reviewed and sources of non-analytic error are "located" within the entire testing cycle. Reference sources are presented.
mesh_terms: D000704:Analysis of Variance; D007753:Laboratories / Q000592:standards*; D011786:Quality Control; D012016:Reference Values