January 2010
Feature Story

Anne Ford

“Laboratory performing a high volume of esoteric testing seeks same to exchange samples for alternative proficiency purposes. Must enjoy fulfilling accreditation requirements, avoiding errors, and taking long walks along the beach. Send photo.”

Okay, so you might never find that particular ad on Match.com. But for many laboratories that perform tests for which no proficiency test is available, the basic idea is the same—to find a laboratory with which to exchange samples for alternative proficiency testing. It’s one of the most common ways of performing alternative PT, but is it the best? CAP TODAY spoke with several laboratories about the advantages and disadvantages of sample exchange as a means of solving the alternative PT problem.

Put Jeffrey A. Kant, MD, PhD, in the “pro” column on this one. “Our preference is to do inter-lab exchanges,” he says. That said, he adds, “It is a hassle. There’s no question about that. It takes a fair amount of time to make the contacts, put the samples together, send them out, track the results, follow up on it, review them, and all that.” Dr. Kant is director of the Division of Molecular Diagnostics at the University of Pittsburgh Medical Center and advisor to the CAP/American College of Medical Genetics Biochemical and Molecular Genetics Resource Committee.

Of the tasks he mentions, finding a partner in the first place is often the most challenging. Dr. Kant sometimes looks for exchange partners via a method not unlike online dating—posting a request on the listserv of the Association for Molecular Pathology. “It’s not uncommon to see people put up a posting to say ‘I’m looking for a lab to exchange samples with for such and such a target,’” Dr. Kant says. He also makes use of a directory that is available from the Association for Molecular Pathology of laboratories that perform non-genetic tests, as well as a similar directory for genetic tests (GeneTests) run out of Children’s Orthopedic Hospital, Seattle, under a grant from the National Library of Medicine. And then there’s the old-fashioned method: “Sometimes you just know of certain labs that do a particular test, and you call them up.”

Dr. Kant is not the only one who finds the sample-exchange method preferable but some­times difficult. “It’s always good to have your test verified by another laboratory,” says Iris Schrijver, MD, director of the molecular pathology laboratory at Stanford University Medical Center, associate professor of pathology at Stanford University School of Medicine, and chair of the CAP/ACMG Biochemical and Molecular Genetics Resource Committee. “It’s an independent validation of your result, and in that sense I think it’s preferable. But it can be quite challenging to find an exchange partner for either a really rare test or a very new test.” It’s not just a matter of tracking down a laboratory that performs the same test for which you need alternative PT, she points out. “Sometimes the lab may not be interested in being an exchange partner because they already have an exchange partner.” In that case, a laboratory might resort to actually paying another laboratory for the testing, which can become quite costly, Dr. Schrijver says.

Some laboratory managers, such as James Pettay, MT(ASCP), manager of the Cleveland Clinic’s molecular genetic pathology lab, are so wary of the sample-exchange method that they avoid it altogether. For one thing, “I might not have enough redundant material to provide to other labs,” Pettay says. For another, a partner laboratory “might be a CLIA-certified lab, but are they doing it [a test for which alternative PT is needed] exactly the way we are?” he asks. “Most of the tests we do alternative proficiency for are FISH probes. There are different ways to do FISH and different ways to review FISH results, and they might not do it exactly the way we do it. If I could find another lab that had the same test menu, and we could just swap samples at no cost to each other, I guess that would be an acceptable way of doing it. But it’s hard to find another laboratory out there that’s got the time and personnel to do that. That’s why we decided on in-house blind testing” instead.

Agendia Inc., of Huntington Beach, Calif., manufacturer of the FDA-cleared in vitro diagnostic multivariate index assay MammaPrint, performs interlaboratory PT (on top of its intralaboratory PT) by exchanging samples with a sister laboratory at the company’s headquarters in Amsterdam. “Because to date there are no other commercial microarray-based tests, we are not yet able to exchange samples with other labs,” explains Miriam Reyes, manager of laboratory operations. “The advantage of exchanging samples with Amsterdam is that we have the same procedures.” She and others at Agendia hope that as microarray-based testing becomes established, more proficiency testing options will become available.

The final word may be that sample exchange simply “works better in some situations than others,” says Washington C. Winn Jr., MD, MBA, professor of pathology at the University of Vermont College of Medicine and director of the clinical microbiology laboratory at Fletcher Allen Health Care, Burlington. In his view, alternative proficiency testing by means of sample exchange is more easily done when the laboratories doing the exchanging are in reasonably close physical proximity. “We’re the only big hospital in the state, and we’re sort of remote, so it’s not so easy,” he says. “If we were in a big city and there were six hospitals, it would be relatively easy to get together and develop a shared testing platform. It makes it a lot easier if you’re not mailing across state lines. So we don’t actually use that mechanism very much, if at all.”

In microbiology, Dr. Winn continues, “CAP has been sufficiently on the ball that now pretty much everything is covered by a proficiency testing product,” so he seldom finds himself needing to perform alternative PT anyway. When he does, he, like Pettay, uses the double-blind internal testing method. “So the only thing we miss is the peer analysis. But of course, if you’re exchanging with just one other lab, you don’t really have peer analysis either,” he says.

In recent years, the CAP has sought to remove some of the obstacles to performing alternative PT via interlaboratory sample exchange. In late 2007, it launched the Internet-based Registry Service for Genetic Testing, which is designed to help laboratories that perform low-volume genetic tests find exchange partners for alternative PT. A laboratory seeking an exchange partner for a particular test can register with the service; as soon as three laboratories are registered as performing the same test, the CAP facilitates contact. After the laboratories exchange and analyze their samples, they send the results to the CAP, where the proficiency data are anonymized and summarized in a report sent to each lab. So far about 60 laboratories have registered for the service, of which 26 have been connected with exchange partners. At CAP TODAY press time, the College was in the process of relaunching and expanding the service under the new name of the Sample Exchange Registry for Alternative Assessment.

One side benefit of the registry: By looking at the tests for which laboratories most request exchange partners, the College will be able to determine which analytes are in most need of CAP Surveys. Says Dr. Schrijver: “It is one way to identify where there really is a need and where formal proficiency testing should be developed.”