Proficiency testing of analytical laboratories: organization and statistical assessment

Abstract

Proficiency testing is becoming an integral feature of laboratory accreditation, which itself is now being advocated as a result of the development of the European Community Certification and Accrediation Policy. In analytical science, proficiency testing involves the regular circulation of test materials for analysis in the participating laboratories, and the subsequent assessment of the resulting data by the organizing body. It plays a vital role in the achievement and maintenance of appropriate data quality, in combination with the use of certified reference materials, validated methods and data quality control. In this report the technical background and organization of proficiency testing are presented, together with statistical methods for interpreting the results. Because of the rapid proliferation of proficiency testing schemes, it is recommended that anlytical chemists move towards a unified approach to the presentation of results from trials, so that the meaning of the results of all schemes is immediately apparent. This is best achieved by the use of standard elementary statistics. Specific recommendations are given and a specimen protocol is appended.