4.2 External quality assessment

An external quality assessment (EQA) compares the performances of different laboratories. A proficiency testing scheme (PTS) is the most cost-effective and useful EQA method. PTS involves regular dispatch of test isolates to laboratories, to be processed using the normal testing methods by staff who routinely handle such samples. Results are analysed by a reference laboratory which provides feedback and allows comparison with results from other participating laboratories.

If participation in a formal PTS is not possible, other means of assessment of quality may be achieved through a combination of within-country retesting/rechecking by a reference laboratory and internal QA with periodic external observation of practices and procedures by qualified personnel (WHO 2011a). Another option is for interlaboratory comparison to compare results and interpretation.