The Lab Says It’s Cancer. But Sometimes the Lab Is Wrong.


Ultimately he had his prostate removed. “I said, ‘Mistakes happen,’” Mr. Karman said.

They may be happening more often than doctors realize. There is no comprehensive data on how often pathology labs mix up cancer biopsy samples, but a few preliminary studies suggest that it may happen to thousands of patients each year.

Fortunately, there is now a high-tech solution: a way to fingerprint and track each sample with the donor’s own DNA.

But it costs the patient about $300 per sample, and labs have been slow to adopt it, saying that the errors are rare and the test too expensive, and that they have plenty of checks in place already to avoid mix-ups.

Dr. John Pfeifer, vice chairman for clinical affairs in the pathology and immunology department at Washington University School of Medicine in St. Louis, who has studied the problem, is not quite so sanguine.

“All the process improvement in the world does not get rid of human errors,” he said. “Millions get biopsies every year. Is society going to say, ‘Yeah, mistakes happen but we’re not going to look for them?’”

The fingerprinting method, offered by Strand Diagnostics, is simple: A doctor gets a DNA sample by swabbing inside a patient’s mouth. It is sent directly to Strand with a bar code identifying the patient.

That bar code is also used to label the patient’s biopsy. If it shows cancer, the pathologist sends the biopsy cells to Strand. The lab matches the DNA from the swab to that of the biopsy cells.

If these DNA fingerprints did not match, that signaled a lab mix-up. That was how pathologists discovered that samples from Mr. Erickson and Mr. Karman had been switched.

Despite the best efforts of pathologists to avoid these mix-ups, hints of trouble have been turning up for years.

In 2011, researchers conducting a large clinical trial reported that two men who were found to have prostate cancer — and who had their prostates removed — did not have the disease at all.

Instead, their biopsy samples had been mishandled. (A third mix-up was caught before any action was taken.)

The researchers then performed a rigorous DNA analysis of more than 10,000 biopsies taken during the period. Twenty-seven were mislabeled. Among 6,733 blood samples, 31, or 0.5 percent, had been switched.

The percentage of errors may not be high. But each one may lead a patient down a life-altering path, to a grueling treatment that was unnecessary, or to the neglect of a cancer that may or may not prove deadly.

Pathologists see lab mix-ups routinely, but often the mistake is obvious — a sample supposed to be from a brain actually is from a lung, for example.

“You say, ‘O.K., yeah, there’s been a mistake,’” Dr. Pfeifer said. “I don’t know many pathologists who haven’t had that occur.”

But what about mix-ups that are not so obvious — two lung tissue samples that are switched, or two breast samples? Dr. Pfeifer turned to DNA fingerprinting to determine how often such samples are mixed up at Washington University.

Photo

Merlin Erickson was told he had cancer after a pathology lab mixed up his biopsy with another patient’s.

Credit
Nate Pesce for The New York Times

He found a few errors. One man’s lung tissue was cancerous, but DNA analysis showed the lung cells were not his.

Another patient had a liver biopsy that showed cancer, but the cells were from somebody else. Still another man was mistakenly thought to have advanced aggressive prostate cancer; again, DNA showed the tissue was somebody else’s.

To really get an idea of the frequency of these mix-ups nationwide, however, Dr. Pfeifer needed a large database.

Ted Schenberg, the chief executive at Strand, offered to supply the data: more than 13,000 biopsy results from men evaluated for prostate cancer at a number of laboratories.

Dr. Pfeifer agreed to review data, although he knew the company had a significant financial interest in the outcome. To minimize conflicts of interest, Mr. Schenberg would not pay him to do the work and would not be involved in the analysis.

Dr. Pfeifer documented two types of errors in this large sample: an “absolute switch,” in which one patient’s tissue was mixed up with another’s. And a “partial switch” in which some of one patient’s cells ended up mixed in with cells from someone else.

“Every lab had both of these errors,” Dr. Pfeifer said. In general, the rates were low — .26 percent of samples were absolute switches, and 0.67 percent were partial switches.

But the rates were slightly higher among independent labs, including large commercial companies that handle huge numbers of specimens: 0.37 percent were absolute switches, and 3.14 percent were contaminated.

Remedying these infrequent errors is a costly endeavor. Most private insurers are willing to cover the testing; it’s far less expensive than paying for unnecessary treatment, or treatment late in the course of a disease that should have been identified sooner.

Medicare, on the other hand, does not cover DNA fingerprinting of biopsies, and many of patients receiving cancer biopsies are older. (Legislation introduced in Congress in May would require the program to cover the service, but only for prostate biopsies.)

Consumers may request DNA fingerprinting themselves, but there is no guarantee that the pathology lab to which their biopsies are sent will offer the service.

Recently, a group of researchers led by Dr. Kirk Wojno, a pathologist at the Comprehensive Urology and Comprehensive Medical Center in Royal Oak, Mich., decided to address the financial obstacles to widespread DNA testing of biopsies, in this case specifically for prostate cancer.

Unnecessary treatments and lawsuits come with a high price tag, the researchers concluded.

There are about 806,000 prostate biopsies a year in the United States. Lab mix-ups of these biopsies alone cost the nation about $879.9 million per year. That figure includes cost of lawsuits that result from mix-ups.

The cost of doing DNA fingerprinting, Dr. Pfeifer argues, “is well within the range of costs we see with other clinical testing.”

”You can make an argument that for prostate cancer you should probably do this for every patient at the time of initial diagnosis,” he added. “By extension, you probably have the same situation for other diseases.”

But other experts are not convinced the test is worth the cost.

While mix-ups do happen, pathologists have put a series of steps in place to try to avoid them, including 26 requirements for labeling containers and identifying patients, and ordering tests, said Dr. Raouf Nakhleh, vice chair of the College of American Pathologists’ Council on Scientific Affairs and a professor of pathology at the Mayo Clinic in Jacksonville, Fla.

“We get paid $125 to process a specimen and produce a diagnosis,” he said. He turns to DNA fingerprinting only when he suspects a mix-up — for example, a clinical exam is at odds with a pathology report.

Dr. Jennifer Hunt, who chairs the Department of Pathology at the University of Arkansas for Medical Sciences, also objects to the cost. “It’s related to finances,” she said. “And the risk of error is extraordinarily low.”

Dr. Sanford Siegel of Chesapeake Urology used to feel the same way. But in 2015, a new patient had a blood test that indicated he might have prostate cancer. He had a biopsy, which confirmed it.

The man had his prostate removed — only to learn he had been the victim of a lab mix-up. His reaction, as Dr. Siegel recalled? “I am calling a lawyer.”

After that, Chesapeake Urology made the DNA test mandatory.

Correction: June 28, 2017

An earlier version of this article misstated the percentage of blood samples, out of 6,733, that were switched in a clinical trial in 2011. It was 0.5 percent, not 0.05 percent.

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