Clinlab Navigator

Biotin Interference with Immunoassays

Biotin is a coenzyme and a B vitamin that occurs naturally in many foods. Wheat germ, whole-grain cereals, whole wheat bread, eggs, dairy products, peanuts, soya nuts, Swiss chard, salmon, and chicken are all sources of biotin. The Institute of Medicine recommends a daily intake of 30 mcg for adults.

In spite of this official recommendation, many people have begun taking high dose biotin supplements because of marketing claims that it can strengthen keratin and improve hair, nails, and skin. These supplements may be labeled as vitamin B7, vitamin H, or coenzyme R and contain more than 300 times the recommended daily dose. For example, Costco sells Kirkland Signature Hair Skin and Nails that contains 5000 mcg of biotin per pill. Sam’s Club sells Members Mark Biotin 1000 mcg with Keratin 100 mg. Other popular brands are Nature’s Bounty Hair Skin and Nails and Natrol Biotin.

In January 2016, the Endocrine Society alerted its members that megadoses of biotin could interfere with immunoassays that incorporate biotin and streptavidin into their immunoassay design. Biotin interference can produce either falsely high or low results, depending on immunoassay format. In general, biotin causes falsely high results in competitive immunoassays and falsely low results in immunometric immunoassays. The degree of interference may vary by immunoassay manufacturer.

A letter to the editor published in the August 18th issue of the New England Journal of Medicine described 6 children who were taking high-dose biotin supplements for inborn errors of metabolism. These children had falsely elevated results for free T4 and free T3 and falsely decreased results for TSH and thyrotropin receptor antibodies. This combination of erroneous results was suggestive of Graves’ disease. All results normalized after biotin was discontinued.

A more recent article published in the October 27th issue of the New England Journal of Medicine reported falsely elevated results with competitive immunoassays for free T4, free T3, testosterone, estradiol, progesterone, DHEA sulfate and vitamin B12. They also reported falsely decreased results for immunometric immunoassays for TSH, PSA, PTH, luteinizing hormone and follicle stimulating hormone.

Biotin has a very short circulating half-life of two hours. It should be cleared from the circulation within 5 half-lives. The authors recommended that patients taking biotin supplements should refrain from taking them for 72 hours before having their blood drawn for laboratory tests.

Kummer S. Biotin treatment mimicking Graves’ disease. N Engl J Med August 18, 2016;375:704-6.

Trambas CM et al. More on biotin treatment mimicking Grave’s Disease. N Engl J Med. October 27, 2016;375:1698.

AddThis Social Bookmark Button