Proficiency Testing

Proficiency testing (PT) is one external measure by which a laboratory's performance can be judged. In a PT program, laboratories are sent samples for analysis and return their results to the PT program organizers. The correct result (or range of results) for these programs is determined by the organizers based on a comparison of participant results with results obtained by reference laboratories (accuracy-based grading), or by comparison with other laboratories that use the same analytical methods (peer-group grading). Ideally, all PT programs would use accuracy-based grading, but there are significant practical limitations to this approach. One of the major limitations is the PT material itself. For many analytes it is not possible to obtain the necessary range of concentrations to test low, normal, and high concentrations using real human samples. This necessitates the use of artificial samples that have been spiked with the analyte or from which the analyte has been removed (or at least its concentration has been lowered). Such artificial samples may behave unexpectedly when tested using some analytical equipment and give higher or lower values that would be obtained in a native specimen containing the same concentration of the analyte. This is known as the matrix effect. Other limitations may require peer-group grading; for example, recombinant proteins may not be detected equally in different manufacturers' immunoassays, making accuracy-based grading impossible. Enzyme concentrations may be determined by different manufacturers using different concentrations of cofactors, different temperatures, and different substrates, thus giving rise to such inter-method disagreement that accuracy-based grading is impossible.

Molecular testing poses certain challenges to PT programs. It may not be possible to obtain real human specimens such as blood from subjects known to carry mutations of interest because of the quantities required for a large PT program. This necessitates the use of cell lines or even DNA aliquots for PT programs in genetics. Such samples cannot test all phases of the analytical process, including extraction of DNA from whole blood (the normal procedure for genetic testing). The same concern applies to molecular testing for infectious diseases such as HIV-1. For these reasons, it is not uncommon that PT samples do not fully mimic patient samples.

Under the CLIA, laboratories are required to enroll in PT programs for a group of analytes specified in Subpart I of the regulations. These analytes were chosen based on clinical laboratory testing patterns that existed in 1988, and the list has not been updated since then. As a result, many newer tests, including molecular tests, are not on this list. For tests not on this list of "regulated" analytes, laboratories must verify the accuracy of their methods by some other method at least twice a year. This could include comparison of results with those obtained by a different method: sample exchange with another laboratory, or even correlation of results with patients - clinical status. If formal PT programs exist, laboratories should consider enrolling in these. Several of the accrediting organizations do have requirements for participation in PT programs where these exist, including PT programs for molecular testing.

Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

Get My Free Ebook

Post a comment