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Mayo Clinic Lab Directors Take Aim at Biotin Interference in Immunoassays

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NEW YORK (360Dx) – Patients may be consuming greater quantities of biotin, a supplement taken to support the health of their skin, hair, and nails, but as a result, they may also be interfering with some of their own diagnostic test results.

The issue has come to a head for some clinical laboratories, prompting them to develop methods to mitigate the risks associated with inaccurate results from certain immunoassays. As part of their mitigation strategies, lab directors are collaborating with physicians and in vitro diagnostic manufacturers "to raise awareness, but not to raise alarm," Nikola Baumann, director of central clinical laboratory and central processing at the Mayo Clinic, said in an interview.

Test results are sometimes compromised in immunoassays that use biotin-streptavidin reactions within their assays.

A study published in August in the journal Endocrine Practice stated that "the recent, marked increase in the use of over-the-counter, high-dose biotin supplements has been accompanied by a steady increase in the number of reports of analytical interference by exogenous biotin in the immunoassays used to evaluate endocrine function."

The researchers wrote that biotin-related analytical interference is a problem that touches every area of internal medicine, "since immunoassay methods of similar design are also used for the diagnosis and management of anemia, malignancies, autoimmune and infectious diseases, and cardiac damage."

"Based on the volume of consumer advertising that we're seeing, our assumption is that there's an increase in interest or potential use of biotin," and that is contributing to testing issues in laboratories, Brooke Katzman, a codirector of hospital clinical laboratory and point-of-care at the Mayo Clinic, said in an interview.

"Depending on the test method or type of reaction — and whether it's a competitive immunoassay or sandwich immunoassay, for example — biotin affects whether the result is falsely increased or falsely decreased," Katzman said.

In some of their early work on this issue, they noticed that some thyroid-function tests were providing false increases or decreases in results. They saw that in the presence of biotin, the tests mimiced biochemical hyperthyroidism, and "so it's not something that is easily or obviously identifiable to a physician," Katzman added. 

In vitro diagnostics manufacturers have been using the biotin-streptavidin reaction in their assay designs for decades and it's proven very useful, Baumann said, adding manufacturers who use biotin-streptavidin interactions in immunoassay reagents include package inserts warning users that high concentrations of biotin may interfere with the assay results. "This is not something that that the IVD manufacturers have been trying to hide," she noted.

However, adding information to test kits may not be enough of a warning in some circumstances. Physicians may not recognize that biotin has interfered with a test result unless they recognize that a patient's signs and symptoms are not aligned with the results they are receiving from a lab.

"It gets tricky because a physician may or may not question a result depending on how much confidence they have in the lab, or how much they are correlating clinical symptoms with lab results," Baumann said.

Baumann and Katzman have been studying the issue with colleagues at Mayo Clinic since they first confirmed that biotin had interfered with a thyroid hormone lab test in 2015.

Not until recently, however, have laboratories and IVD companies upped the ante on raising awareness.

"Although IVD manufacturers include disclaimers in package inserts with tests, there has been an assumption by many in the field that high-dose biotin was mainly being used by some patients being treated for multiple sclerosis," Baumann said, adding that in clinical studies, investigators have looked at high-dose biotin treatment for these patients.

What had not been recognized, however, was that "a few chewable supplements a day" constitutes a high dose of biotin, Baumann noted. Supplements on the market consist of between 5 and 10 milligrams of biotin, which is a high dose for a laboratory test.

Laboratories are implementing a variety of options to address the issue.

"We've communicated with our clinicians across the Mayo Clinic health system, making them aware that if patients take biotin supplements, they can reach concentrations high enough in the blood to interfere with lab results," Baumann said, adding that "In our system … patients receive instructions for how they should prepare for laboratory tests." The instructions require that patients don't take biotin supplements for at least 12 hours prior to laboratory testing.

Some of the smaller hospitals in the Mayo Clinic health system append comments to the laboratory test results, telling physicians that the test results of patients taking biotin supplements may be inaccurate, and to contact the laboratory if they have any questions, Baumann said.  

Other health systems are attaching warnings to electronic medical records. If a patient lists biotin in her list of medications, the system alerts a physician so that he or she can tell the patient to not consume biotin within a window of time prior to testing.

Katzman said that one concern with this method is that patients don't always accurately report the supplements they are consuming.

In their labs at the Mayo Clinic, Baumann and Katzman are taking additional steps to troubleshoot tests they suspect may have been hampered by a patient's use of biotin. One method is to conduct serial dilutions of the sample and check if the results are linear.

"If there is an interference, you will see inconsistent results from one dilution to the next," Katzman said.

Katzman noted that alternatively, they sometimes test suspect samples on a separate platform that doesn't use the biotin-streptavidin interaction, and they then compare the results.

Katzman said that another option is to deplete the biotin sample before it is tested. The researchers bind up any free biotin in the sample prior to testing in identifying inconsistent results. In this circumstance, the lab directors can't report a result, but they alert physicians when they detect interference, and then measure the sample again using an alternate testing method.

Most important, Baumann said, may be the level of communication ongoing between lab directors and IVD manufacturers.

"As laboratory directors, we have been in constant communication with the in vitro diagnostics manufacturers," she said. "They are responsive and actively working with laboratories to increase awareness and doing additional studies to develop solutions."

It's not an "us-against-them" situation, she said, adding that "We are all working together to try to solve this issue."