Question

What are some concerns with proficiency testing and why?

Answer 1

Proficiency testing determines the performance of individual laboratories for specific tests or measurements and is used to monitor laboratories’ continuing performance.Proficiency testing is also called interlaboratory comparison. As this term implies, proficiency testing compares the measuring results obtained by different laboratories.  It primarily measures accuracy because each laboratory’s results are compared to the interlaboratory mean, which is assumed to be the true value. Each individual laboratory’s accuracy is evaluated by how close its results are to the mean. Proficiency test results are reported as standard deviation indexes (SDIs). SDI is calculated by the following formula:

SDI = (your result - interlaboratory mean)/ interlaboratory SD.

Proficiency Testing (PT) or External Quality Assessment (EQA) is a program in which multiple specimens are periodically sent to a group of laboratories for analysis.

The purpose of any proficiency test (PT) is

• To find out whether you have already got the knowledge and the skills that are taught in a particular course even though you have not taken the course.
• To evaluate the laboratory performance with regard to the testing quality of patient samples.This evaluation is performed by comparison of the results of the PT samples within a group of similar methods, a so-called peer group, and from this comparison determine the performance of the individual laboratory with regard to imprecision, systematic error and human error concerning the PT samples.
• To measured as repeatability and reproducibility. Systematic error is measured as bias. From the performance on PT samples the performance on patient samples are deduced. A PT program will normally only evaluate the analytical phase of patient sample testing. The preanalytical - and postanalytical - phase has to be evaluated using other tools.