Evaluating assay precision

* When evaluating the precision of a method it is necessary to assess the repeatability (within-run) and the total or within-laboratory precision. * It is insufficient to assess repeatability in a single run. * Clinical and Laboratory Standards Institute (CLSI) document EP05-A2 describes the protocols for determining the precision of a method. The precision of a method should be tested at at-least two levels; each run in duplicate, with two runs per day over 20 days. CLSI document EP15-A2 describes the protocols that should be undertaken by the user to verify precision claims by a manufacturer. Precision claims by a manufacturer should be tested at at-least two levels, by running three replicates over five days. * A spreadsheet for assisting with the calculations described in this article is available from the AACB web-site.