For doctors in Vancouver, it was a medical mystery.
They suspected their patient might be suffering from low levels of thyroid hormone because the 54-year-old woman reported weight gain and lethargy.
But the lab tests showed the opposite. Her levels were high. So the doctors sent her to an endocrinologist who did the test again and found the same odd result.
Puzzled, the endocrinologist asked about supplements. Yes, it turned out, the woman was taking a supplement — biotin, also known as vitamin B7. She was told to stop for a week and then get tested again. This time, her thyroid hormone levels were within the normal range.
Although the patient's diagnosis was still a mystery, her doctors were able to rule out a false clue that could have sent them down the wrong path. The patient's thyroid hormone levels were not high at all. Instead, her test results were incorrect.
It is known that biotin supplements can interfere with lab tests, resulting in false positive and false negative results on a wide range of clinically important tests.
But who is taking biotin? the Vancouver doctors wondered. It turns out that a lot of people are using the supplement these days.
When Dr. Morris Pudek at Vancouver Coastal Health did a quick internet search, he realized that biotin supplements are in fashion, with Instagram influencers recommending them for nails and hair growth.
"We are now actually putting warnings on a couple of our more important tests, right with the results, to indicate to clinicians that these results may be falsely affected," said Pudek.
Several foods contain biotin, including meat, fish, eggs, seeds, nuts and some vegetables, including spinach, sweet potatoes, broccoli and cauliflower. Genuine biotin deficiencies are considered to be rare in Canada and the U.S.
"I don't think there's been a really good study to say that biotin will actually help people who have adequate nutrition in the first place," said Pudek.
Biotin could interfere with heart attack test
In the March issue of the BC Medical Journal, the doctors related their experience with biotin and its effect on the thyroid hormone test and called for greater awareness among health-care professionals of the risk of biotin skewing important lab results.
"Infertility testing, thyroid testing and tumour-marking testing could be affected." said Pudek.
More education is needed to raise awareness of the risk, said Dr. Sophia Wong from Vancouver Coastal Health laboratories and another co-author of the paper.
Biotin could also interfere with a blood test that helps to determine whether a patient has had a heart attack, the researchers said.
The U.S. Food and Drug Administration issued a warning in 2017 to patients, health-care providers and lab workers after learning about a patient who died after showing an artificially low level of troponin, which can be released into the blood after a heart attack.
Testing for elevated levels of troponin can help health-care providers make the right cardiac diagnosis. The patient had been taking high levels of biotin, and the lab test was sensitive to biotin interference.
Health Canada conducting 'safety review'
Health Canada has not issued an alert as stark as the FDA's. But the agency requires that products containing high levels of biotin have a statement on the label warning about the risk of lab test interference.
"Health Canada is currently undertaking a post-market safety review of the potential risk for biotin interference with laboratory tests and will take appropriate action, as necessary, to help protect the health and safety of Canadians," André Gagnon, a communications adviser with Health Canada, said in an email to CBC News.
In addition to the potential risk, there are also serious questions about marketing claims of the benefits of taking biotin supplements.
Agencies say evidence is lacking
Health agencies, including the U.S. National Institutes of Health, say there isn't enough evidence to support the claims that biotin improves hair, nails and skin, and that more research is required before it should be recommended for that purpose.
Right now, the product monograph for biotin on Health Canada's website describes it only as "a factor in the maintenance of good health" that helps the body metabolize carbohydrates, fats and proteins.
This is an excerpt from Second Opinion, a weekly roundup of eclectic and under-the-radar health and medical science news emailed to subscribers every Saturday morning. If you haven't subscribed yet, you can do that by clicking here
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