In accordance with ISO/IEC 17043, accredited laboratory tests are undertaken:
Participation at interlaboratory comparisons must be carefully planned by the accredited laboratories as a part of their activities for ensuring the quality of their results.
The accredited Proficiency Testing Scheme at which the laboratory takes part should be as similar as possible to the activities which the laboratory itself usually undertakes, in terms of the sampling of measurements, test materials and types of measurements. Testing activities on samples for the proficiency test must be done using ordinary work processes, without any particular treatments.
The analysis of interlaboratory proficiency test results must be included in the broader quality management system review: the data obtained by these tests will give the laboratory information regarding the conformity of its operations, indicating whether they are satisfactory or if any potential issues emerged requiring correction actions.
During the assessment of the results it is necessary to take into account any measurement uncertainties, especially concerning repeated statistically non-conform results. When this happens it is necessary to discover the causes of the error, which may have passed unnoticed. The laboratory must show that it takes into consideration the results of the circuit, implementing the necessary preventive and corrective actions.
The choice of the laboratory to regularly undergo the checks and evaluations of its measuring activities by means of an accredited proficiency test constitutes a guarantee of quality.
An examination of analytical performance makes it possible to demonstrate objectively that the performance is reliable in the eyes of clients, suppliers, control bodies, accreditation bodies and the regulatory authorities.