The role of proficiency testing in achieving standardization and harmonization between laboratories

Objectives: Proficiency testing is part of a quality system that provides external assessment that a laboratory's performance meets clinical requirements. Design and methods: A set of samples, intended to simulate clinical samples, is provided to a group of laboratories. The samples are measured for specified measurands and the results reported to the organizing body. Target values are assigned by the organizing body typically as the mean response of a group of laboratories that use similar measurement technology;, or, when samples are commutable with native clinical samples, by a reference measurement procedure. Results: Each participant's results are compared to the target values to determine if a laboratory's results are in conformance to the expectations for clinically acceptable results. When commutable samples are used, results can be compared to reference measurement procedure values to evaluate trueness. Unacceptable results are investigated and corrective action taken. Conclusion: Proficiency testing allows an individual laboratory to evaluate if its performance is satisfactory for the intended clinical purpose. Comparison of results among laboratories allows evaluation of the effectiveness of calibration procedures in the field. (c) 2008 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.