Home genetic testing kits overwhelmed with BRCA false positives

Chloe Kent 22 July 2019 (Last Updated July 22nd, 2019 12:45)

Senior doctors have called for a crackdown on the sale of home genetic testing kits, following a surge in the number of patients being wrongly informed they are carrying serious genetic mutations.

Home genetic testing kits overwhelmed with BRCA false positives
Doctors have warned that these inaccuracies are placing an undue burden on primary care services and genetic clinics. Credit: Shutterstock

Senior doctors have called for a crackdown on the sale of home genetic testing kits, following a surge in the number of patients being wrongly informed they are carrying serious genetic mutations.

False flagging of faulty BRCA genes, which indicate a predisposition for breast and ovarian cancers, was the most common issue. University of Exeter analysis of a consumer genetic testing chip found that the test had a sensitivity of only 35% when testing for BRCA1 and BRCA2, meaning when the test gave a positive result it was far more likely than not to be wrong. It did however have a specificity rate of 98%, meaning its negative results were much more reliable.

Exeter researchers also found that another DNA chip was only correct 17% of the time when it detected a cancer-linked BRCA mutation. It also missed over half of those with actual BRCA mutations in a database of 50,000 patients, meaning it could provide false reassurance to patients who do in fact have a mutation.

Doctors have warned that these inaccuracies are placing an undue burden on primary care services and genetic clinics. They are now having to treat an influx of patients alarmed by these false results, often with serious consequences.

One patient was reportedly scheduled for a preventative double mastectomy after being falsely alerted to a BRCA mutation in her home genetic test result, which was called off at the last minute when an NHS laboratory test revealed the test had given a false positive.

Major genetics companies typically offer ancestry testing or health data restricted to just a handful of conditions. Popular testing company 23andMe actually has an FDA-approved test which can detect three BRCA mutations mostly found in people of Ashkenazi Jewish heritage.

However, consumers are then able to download their raw genetic data and send it to third-party companies which will provide results and analysis on thousands of genes for as little as £20. The technology is unfit for the job of detecting rare mutations on a large scale, meaning the results provided to patients can be wildly inaccurate.

Speaking to the Guardian, University of Exeter genomics researcher Caroline Wright said: “The findings are shockingly bad. At the point where they’re this bad, you have to think about not sharing the data. It can be so damaging to the individual if they find out this completely erroneous information.”