Lab testing for the genes that predispose a person to develop cancer is highly complex, both to preform and interpret. For example and relating to BRCA, I have blogged about some of the pitfalls of such testing (see: BRCA Exchange Available on the Web; Understanding BRCA Variants). Here's a quote from this note discussing some of the complexities that are encountered:
It's not known among some healthcare consumers that there are a host of BRCA variants other than the standard ones. Normal BRCA testing looks for three specific genetic variants that are linked to hereditary cancers. Two of these variants — 185delAG and 5382insC — are in the BRCA1 gene. One variant — called 6174delT — is in the BRCA2 gene. A patient may test positive for a variant other than these common ones and it may not be clear under such circumstances what treatment to offer to the patient.
A recent article in the New York Times warns consumers about the fact that the 23andMe BRCA testing may be misleading (see: Don’t Count on 23andMe to Detect Most Breast Cancer Risks, Study Warns ). Below is an excerpt from the article:
In 2010, Dr. Pamela Munster mailed her saliva to 23andMe, a relatively new DNA testing company, and later opted in for a BRCA test. As an oncologist, she knew a mutation of this gene would put her at high risk for breast and ovarian cancer. She was relieved by the negative result. Two years later, after she learned she had breast cancer, she took a more complete genetic test from a different lab. This time it was positive. A study of 100,000 people released earlier this month suggested that this experience could be widespread. Nearly 90 percent of participants who carried a BRCA mutation would have been missed by 23andMe’s test, geneticists found. 23andMe’s testing formula for this risk is built around just three genetic variants, most prevalent among Ashkenazi Jews. The new study demonstrated that most people carry other mutations of the gene, something many doctors have long suspected....
Dr. Munster said that 23andMe was “not doing anything actively deceptive.” But she is still concerned that many customers do not grasp the limits of mail-in genetic testing. 23andMe now has more than 10 million customers. Even if only a small percentage take the test, that’s thousands who could be misled. Mary-Claire King, a professor at the University of Washington who discovered the region on the genome that became known as BRCA1, had a more blunt assessment of the Food and Drug Administration’s decision to allow the test....“The F.D.A. should not have permitted this out-of-date approach to be used for medical purposes,” Dr. King said. “Misleading, falsely reassuring results from their incomplete testing can cost women’s lives.”
For me, the fundamental question here is whether consumers "can be trusted" to order lab tests and interpret the results without physician intermediation. I have blogged frequently on this subject (see, for example: Comparison of "Traditional" Lab Testing with Direct Access Testing; An Estimate of the Size of the Direct Access Testing (DAT) Market). The excerpt from the article above focuses on an oncologist who seems to have been lead astray by a negative BRCA test from 23andMe, assuming that she was negative for any BRCA variant. I suspect that Dr. Munster was chosen as the focus of this story to make the point that the interpretation of the BRCA test results is so complex that even an oncologist, ordering the test for herself from 23andMe, could misinterpret the result.
I believe that allowing consumers to order certain routine lab tests for themselves is desirable because I also think that it will result in a general improvement in public health. Some people are too busy or not predisposed to visit a physician frequently. For them, ordering lab tests on the web may improve their health status. The pivotal issue in this discussion, then, is how laboratory tests should be reported to consumers. The most complex tests, particularly those requiring complex interpretation, should not be directly available to consumers. Consumers will generally not be lead astray by the performance of common lab tests but must be provided with reference ranges and instructed to seek the help of a physician for results that fall outside of normal ranges and/or when they have symptoms of a disease.
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