On The Shelf
Mary Warner
FDA recently updated its 2017 safety communication to remind the public, health care providers, lab personnel, and lab test developers that biotin, often found in dietary supplements, can significantly interfere with certain lab tests and cause incorrect results that may go undetected.
Biotin, also known as vitamin B7 or vitamin H, is a cofactor for five carboxylases (propionyl-CoA carboxylase, pyruvate carboxylase, methylcrotonyl-CoA carboxylase, acetyl-CoA carboxylase 1, and acetyl-CoA carboxylase 2) that catalyze critical steps in the metabolism of fatty acids, glucose, and amino acids. It is often recommended as a dietary supplement to strengthen hair and nails.
The daily recommended intake for an adult is 30 µg, but many biotin supplements contain much higher doses, ranging from 5,000 µg to 10,000 µg.
Many lab tests, particularly those used to diagnose thyroid and heart disease, use biotin immunoassay technology and are potentially affected by biotin in a patient’s blood sample.
FDA is particularly concerned about biotin interference causing a falsely low result when testing for cardiac troponin, a protein normally present in very small amounts in the blood, but for which blood levels increase during and after a cardiac event. The more damage to the heart, the greater the concentration of cardiac troponin in the blood.
Testing for cardiac troponin
Immunoassays that use a streptavidin–biotin interaction step are often used to test for cardiac troponin, and in such assays, excess biotin could bind the streptavidin, blocking binding of the cardiac troponin–antibody complexes. This may lead to a falsely low cardiac troponin result if the patient has a high level of plasma biotin, resulting in a missed diagnosis of myocardial injury, including myocardial infraction, due to underestimation of cardiac troponin. Standard multivitamin levels of biotin (30–60 µg) pose no risk of interference with these tests.
According to FDA, some lab test developers have been successful at mitigating the biotin interference in their assays since the 2017 FDA safety communication, but others have not yet addressed it.
These manufacturers advise a biotin washout period of several hours to weeks prior to sample collection to avoid biotin interference. But for time-sensitive tests, such as those for the increased levels of cardiac troponin that result from myocardial injury, a washout period is not feasible.
FDA has continued to receive adverse event reports indicating that biotin interference caused falsely low troponin results.
To increase transparency about this issue, FDA created a website to notify the public and health care providers about troponin assays that have not addressed the risk of biotin interference. The site contains a table listing 17 cardiac troponin diagnostic tests that are subject to biotin interference but whose manufacturers have not addressed this risk.
What to tell your patients
Patients will likely not report biotin supplements to their physician or pharmacist—and may not realize they are taking biotin, especially when taking products labeled as beneficial for hair and nails. Even when biotin supplements are reported, neither patients nor physicians may be aware of biotin interference in laboratory immunoassays for cardiac troponin.
FDA recommends that health care providers talk to patients about any supplements or multivitamins they are taking that may contain biotin. Make sure patients understand that biotin is found in some unexpected products, especially those intended for hair, skin, and nails, in levels that may interfere with lab tests, and that they should report this biotin use to their physician before getting any recommended blood tests.