Analytical performance specifications for external quality assessment – definitions and descriptions

Abstract

External Quality Assurance (EQA) is vital to ensure acceptable analytical quality in medical laboratories. A key component of an EQA scheme is an analytical performance specification (APS) for each measurand that a laboratory can use to assess the extent of deviation of the obtained results from the target value. A consensus conference held in Milan in 2014 has proposed three models to set APS and these can be applied to setting APS for EQA. A goal arising from this conference is the harmonisation of EQA APS between different schemes to deliver consistent quality messages to laboratories irrespective of location and the choice of EQA provider. At this time there are wide differences in the APS used in different EQA schemes for the same measurands. Contributing factors to this variation are that the APS in different schemes are established using different criteria, applied to different types of data (e.g. single data points, multiple data points), used for different goals (e.g. improvement of analytical quality; licensing), and with the aim of eliciting different responses from participants. This paper provides recommendations from the European Federation of Laboratory Medicine (EFLM) Task and Finish Group on Performance Specifications for External Quality Assurance Schemes (TFG-APSEQA) and on clear terminology for EQA APS. The recommended terminology covers six elements required to understand APS: 1) a statement on the EQA material matrix and its commutability; 2) the method used to assign the target value; 3) the data set to which APS are applied; 4) the applicable analytical property being assessed (i.e. total error, bias, imprecision, uncertainty); 5) the rationale for the selection of the APS; and 6) the type of the Milan model(s) used to set the APS. The terminology is required for EQA participants and other interested parties to understand the meaning of meeting or not meeting APS.

Strategies to define performance specifications in laboratory medicine: 3 years on from the Milan Strategic Conference

“…The TFG-PEQAS has recommended the use of one of the PS models from the Milan conference [24]. In agreement with Infusino et al [25], the addition of PS derived from Milan models to the EQAS categorization previously published by Miller et al [26] as criteria to evaluate the performance of laboratories participating to EQAS should be promoted.…”

“…The TFG on Performance Specifications for EQAS (TFG-PEQAS) has identified six basic elements that need to be considered: (a) the nature of the EQAS material, including its commutability, which may affect the result interpretation; (b) the procedure used to assign the target value; (c) the data set to which PS are applied; (d) the analytical property being assessed (i.e. TE, bias, imprecision); (e) the rationale for the selection of the PS; and (f) type(s) of model used to set PS [24].…”

“…Miller's categories 1 and 2, which fulfil the metrological requirements (commutable samples, valueassigned with reference measurement procedure), should be each split in two sub-categories: 1/2A, in which Milan models 1 and 2 for PS are applied, and 1/2B, in which other low-order models to establish PS are employed [25]. As initial steps, the TFG-PEQAS encourages EQAS organizers to provide structured descriptions of PS and to review PS providing their rationale; in a more consolidated manner, they recommend developing common EQAS PS through a collaborative process and using relevant Milan model(s), in order to support uniform performance and high quality in the total examination process [24].…”

A pilot study to introduce a local external quality assurance scheme for D‐dimers in the National Health Laboratory Service, in South Africa

“…Quality parameters should be implemented across the whole laboratory network . EQA or proficiency testing (PT) monitors laboratory performance, flagging deviations in quality, and is a valuable tool for identifying and assessing the technology in use across laboratory networks . In addition, it can identify training requirements.…”

Analytical quality: an unfinished journey

“…Available data from external quality assessment schemes (EQAs) highlight the need for further efforts to improve analytical performances. Clinical laboratories using standardized diagnostic systems still provide significantly different results, and appropriate analytical performance specifications for setting and monitoring analytical goals have yet to be homogenously adopted [22]. Analytical quality continues to be the "core business" of laboratory professionals, but only by raising our awareness of the inter-relationship and inter-connection between the different phases of the testing cycle can we hope to improve upon the ultimate value and quality of laboratory information.…”