New study boasts 90% accuracy when using PARR to diagnose canine lymphoma

Who measures the measurements? Who diagnoses the diagnostics? In short, who assays the assays?

Veterinarians have been using polymerase chain reaction for antigen receptor rearrangement (PARR), a readily available molecular assay that helps diagnose some kinds of canine lymphoma, for years. But no one really knew how accurate those assays were—because none have undergone a truly rigorous benchmarking study to determine the accuracy of PARR assays in general, regardless of the manufacturer.

Until now.

In a study published in the Journal of Veterinary Internal Medicine, Ethos Veterinary Health, Ethos Discovery, and the Translational Genomics Research Institute (TGen) found that their version of the test, called ePARR, was more than 90% accurate among a range of lymphoma sample types.

The results of the ePARR test study are based on an analysis of 180 dogs with cancer. The researchers used ePARR to confirm whether the dogs in the study had lymphoma and then to determine what type they had.

“We’re very excited about it,” Chand Khanna, DVM, PhD, DACVIM (Oncology), DACVP (Honorary), told NEWStat. Khanna is chief science officer of Ethos Veterinary Health, president of Ethos Discovery (a 501(c)3 independent not-for-profit incubator of scientific innovation), and co-senior author of the study.

Khanna emphasized that ePARR is not a new kind of assay but rather a new brand of assay, and the way it works to diagnose lymphoma isn’t different from what’s currently out there. He said the big takeaway here is the accuracy of the new study, which he calls “very rigorous.” He pointed out that the sheer number of dogs tested “well exceeds what has been done” in previous studies.

“What’s new is that doctors can offer [PARR assays] with a greater confidence in the performance of the assay than was possible before,” Khanna said.

Most dogs with lymphoma can be easily diagnosed using a simple microscopic evaluation of cells taken from the lymph node, so PAAR isn’t a first-line diagnostic test. However, a small minority of dogs yield tissue samples that display unusual features under the microscope, which makes some clinicians hesitant to begin treatment for lymphoma. In those cases, Khanna said, “you need a much more rigorous confirmatory test.”

PAAR, for example.

NEWStat asked Barbara Biller, DVM, DACVIM, retired associate professor of oncology at the Flint Animal Cancer Center at Colorado State University and practicing veterinarian at Boulder Road Veterinary Specialists in Lafayette, Colorado, what the study meant for veterinarians dealing with suspected cases of canine lymphoma.

“It’s further validation of [PARR],” Biller said. “We don’t need it to diagnose most cases of lymphoma but when we do need it, it can be really helpful. [The study clears up] some of the questions we have as far as how accurate it is for different samples.”

“This is the kind of data we need in this profession,” Biller added. “You have an organized, systematic evaluation of a technique. And it’s really good to see that kind of research.”

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