Ceri Parfitt and Annette Thomas recount a recent study to review the strengths and weaknesses of different models for determining analytical performance specifications. The study used historical data to determine what was achievable in a real-world environment to establish clinically appropriate APS for several serum chemistry analytes.
In terms of external quality assessment (EQA), analytical performance specifications (APS) are defined as a range of values around the target which is considered acceptable for the performance of that test.1 A result outside the acceptable range should alert the laboratory that their assay may produce results that are at risk of detrimentally affecting clinical decision-making. APS provides a simple tool to allow a rapid, standardised assessment of EQA results in both numerical and graphical report formats. Laboratories and point-of-care test (POCT) users must ensure that the analytical quality attained for that test is appropriate for the needs of the clinical service and the clinical utility of the test. Use of the distribution standard deviation limits around the peer group mean may imply acceptable performance for laboratories, but these may not be clinically relevant, resulting in increased risk of patient misclassification. It is therefore essential that EQA performance specification also reflects the clinical need and utility of the test.
Defining performance goals – a hierarchical approach
In 1999, the World Health Organization (WHO), International Federation of Clinical Chemistry (IFCC) and International Union of Pure and Applied Chemistry (IUPAC) met in Stockholm to develop a hierarchy of five approaches for establishing performance goals.2 These were refined at the EFLM Milan strategy in 2014 as three models:3
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