DNA test helps doctors avoid false positive cancer diagnoses

Imagine being told you have cancer – only to learn that your biopsy had been contaminated or mixed-up with someone else’s.

This scenario happens to approximately 3,000 women who undergo breast biopsies every year – or one out of every 100 cases.

“And for every false positive there’s a false negative,” Dr. Andrew Kenler, an assistant clinical professor of surgery at Yale Medical School, told FoxNews.com.  “When you tell a woman she doesn’t have breast cancer but she does, 6,000 patients a year (could) be under or over treated.”

So how exactly do these errors occur?

The process of taking a biopsy, sending it to a lab for analysis and then getting the results back can be complex, often comprised of as many as 15 to 20 different steps. Because of these intricacies, specimens have the potential to be mislabeled or contaminated along the way.

“Pathology labs may do 40 or 50 breast cancer (tests) a day and they will use these kind of vats where they place the slides all together,” Kenler said. “So there is the opportunity, as these cases are being analyzed, for cells and tissue from one patient to contaminate cells and tissue from another patient’s slides.”

Fortunately, Kenler said there is an easy method available to prevent these often devastating mistakes: DNA testing.

“The way we prevent these errors now is using this kit called the ‘Know Error’ system where at the time of the core biopsies a swab is taken from the patient’s cheek,” Kenler said. “We use that swab as a reference sample. It’s basically a DNA fingerprint of the patient.”

Using the Know Error test, each patient’s biopsy can be compared to their DNA sample to ensure that the results are 100 percent accurate.

“If there’s a mismatch we now know, based on this sophisticated, intelligent and fairly inexpensive test, that there must have been an error or contamination,” Kenler said.

The test is easy and stress-free, according to Mary Beth White, 48, a police officer in Shelton, Conn., who was treated by Kenler after being diagnosed with stage one breast cancer in the spring of 2012.

“It was really very simple – it was just a mouth swab. A typical DNA test that you see on every TV show there is now, just a swab,” White told FoxNews.com.

Perhaps even more importantly, taking the extra precaution of utilizing a DNA test can put patients at ease.

“It gave me real peace of mind to know everything was in line the way that it should be, that there was no question,” said White, who now has a clean bill of health after undergoing a lumpectomy and a round of chemotherapy.

Despite the fact that the test is relatively inexpensive, Kenler points out that the Centers for Medicare and Medicaid Services (CMS) refuses to cover it.

“It’s frustrating for me to now have this test not be paid for by Medicare – most third party payers are paying for it, as they should,” Kenler said.

Breast cancer is the second most common cancer in women in the United States, and 1.6 million biopsies are done per year, according to Kenler.

“Most women want this; I have patients ask for this,” Kenler said. “They don’t want surgery until they know they truly have breast cancer.”