PROFICIENCY TESTING AND LABORATORY ACCREDITATION

Proficiency testing (PT) programs are type of an external quality assessment in which simulated patient specimens made from a common pool are analyzed by the laboratories enrolled in the program. The results are then evaluated to determine the quality of each laboratory’s performance. Government and licensing agencies increasingly use PT as a method for accrediting laboratories thereby giving them official authorization to operate. The performance characteristics of PT programs for detecting bias and imprecision are evaluated using methods similar to those as assessing internal QC. 

A common evaluation criterion is comparison of PT test results with those of peer groups, considering all values that exceed 2SD to be unacceptable. To be totally successful a laboratory should produce correct results on 4 out of 5 specimens for each of the analytes and have an overall score of at least 80% for 3 consecutive challenges. If a laboratory has 2 or more incorrect results for any analyte or has an overall score <80% on tow of 3 consecutive surveys, it is suspended. 

For PT the sample are made by agencies which has target value established by definitive or reference methods. If definitive method is not available a comparative method may be used. If the method group is <20 participants, target value means the overall mean after outliers removal. Or in absence of definitive method, then peer group mean values or groups of methods that agree with the definitive method can be used. This target value is termed the definitive method corrected target value (DMCTV).