College of American Pathologists
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  For new analytes, expanded PT exchange


CAP Today




May 2012
Feature Story

Ed Finkel

More than four years after the Sample Exchange Registry for Alternative Assessment got its start, the CAP is taking an all-inclusive approach and expanding the service to all clinical laboratory disciplines.

The CAP in 2007 launched the Internet-based exchange for molecular genetic testing for which no formal proficiency testing was available. Based on laboratory participation in the registry and thanks to the work of the CAP scientific resource committees, the College has since introduced formal PT for KRAS, BRAF, and EGFR, in which many laboratories are enrolled.

“It’s proven its efficacy. It’s been very well received in the molecular field,” says R. Bruce Williams, MD, of Delta Pathology Group in Shreveport, La., and chair of the CAP’s Council on Scientific Affairs. “We saw no reason not to expand this service so that anybody can use this same mechanism.”

Dr. Williams notes that new analytes are being developed all the time and, particularly at first, proficiency testing options are limited to internal assessment or searching for other alternative ways to perform an assessment.

“Especially with newer fields, like genetic testing… it makes it more convenient for everybody who would like to find an alternative means of doing proficiency testing,” he says, adding that he also sees some of the non-molecular cytogenetic tests as those for which interest is likely to be high.

“Drug testing is another possibility,” he says, “and folks doing research into new markers for disease identification treatment and therapy would be another area.”

When at least three laboratories have registered for the same marker, the CAP facilitates an anonymous and confidential exchange. Laboratories test and send their results to the CAP. In turn, the CAP anonymizes the data it receives and sends each laboratory its results, with an anonymous summary report of all the participants’ data. Any laboratory can participate in the program or donate materials.

Through the registry, the CAP now offers “alternative” proficiency testing for the following: PAI-1 (4G/5G polymorphism), MTHFR A1298C, PLA1/A2 (human platelet antigen HPA), mitochondrial DNA mutations, MECP2/Rett syndrome, alpha-thalassemia, MCADD (ACADM gene), APO E, alpha-1-antitrypsin, and HLA-B*5701. Two of them—MTHFR A1298C and MCADD (ACADM gene)—will be offered as formal proficiency testing in 2013. Others could be introduced as formal PT in subsequent years as enrollment grows.

James Prescott, PhD, HCLD, molecular diagnostics director at PathGroup Labs in Nashville, says his lab decided to participate in the exchange because it can’t find commercial specimens for some analytes—and repeat testing for blind specimens is a good practice but not optimal.

“You’re measuring how reproducible your own results are,” he says. “If you have a systematic problem, you’re not going to pick it up. We wanted a way to easily find other ways of doing similar assays.”

Laboratories can find partners through industry meetings and the like. “But having a single point of contact that can get everybody organized and spread out contact information has been fantastic for us,” Dr. Prescott says. “The CAP proficiency testing, as great as it is, it’s very difficult for proficiency survey [providers] to develop materials for some of these [analytes] that maybe only 20 or 30 labs in the country are testing.”

Dr. Prescott can imagine PathGroup Labs using the exchange for other types of testing now that it’s available. The clinical laboratory will be interested, he predicts, and he intends to raise the issue with those in immunohistochemistry.

“The clinical lab is more straightforward, a much more mature industry, so I don’t know how much they’re going to participate, but they’re definitely going to look at it,” he says. In immunohistochemistry, “I wouldn’t be surprised if we have antibodies that are difficult. In general, the operation is going to be looking at the Sample Exchange Registry to see what we can do to help with our proficiency testing.”

More broadly, Dr. Prescott sees a variety of benefits for laboratories and patients in the expansion of the registry. “It’s incumbent on us to make sure we know the tests we’re reporting are accurate, specific, and within whatever criteria we can,” he says. “Being able to compare our results across methodologies is just a great example of scientific reproducibility. … It’s one less thing physicians need to worry about with more rare analytes.”

For the laboratory community, the system allows an external check on performance for testing a particular analyte, Dr. Williams says. “This will give the participating laboratory the best option for alternative assessment for an analyte performed by very few. For patients, external proficiency testing provides the extra confidence in the accuracy of their test results.”

When it comes to patients and payers, the system will be “completely invisible,” Dr. Prescott says. “It’s hopefully going to bring a lot of peace of mind for our downstream customers that we are doing the proper verification of our assays. Incorrect diagnoses and poor results from the laboratories are definitely a huge cost factor. Being able to provide yet another level of assurance that the laboratory results are accurate is going to be good for everybody.”

Ed Finkel is a writer in Evanston, Ill. Those interested in participating should visit to fill out a contact form and then, when the lab has a sample ready to exchange, the material submission form.