Jul 20, 2022 | 5 min read
Biotin gained its notoriety when in 2017, the FDA issued a warning to health care providers and clinical laboratories about biotin interference in assays that use biotin technology. The warning indicated that patients taking biotin supplements were susceptible to receiving false results for a number of laboratory tests.
How does biotin interfere with lab tests?
Immunoassays were specifically mentioned in the warning as a number of vendor immunoassays incorporate biotin with streptavidin in an antigen/antibody binding format in their design. The effects of the interference can include falsely decreased or falsely increased results. Immunoassays that incorporate streptavidin–biotin binding span the gamut and may be vendor specific but include assays such as free thyroxine, ferritin, testosterone, prostate specific antigen, troponin, and others.
Vendors affected by biotin binding characteristics have had to consider their own response to this issue, including enhancing current assays, employing new unaffected methodologies, or using pre-treatment techniques to reduce sample biotin levels. Similarly, clinical laboratories have had to develop ways to handle and mitigate potential biotin interference in instrumentation that uses biotin technology.
Immunoassays affected by biotin (TSH, free thyroxine, troponin, etc.) have variations in the threshold level at which there is interference with test results. Some assays have interference thresholds as high as 10,000 ng/mL, whereas other assays have lower interference thresholds of only 5 ng/mL. This is problematic given that some studies have shown serum biotin concentrations in supplementing individuals to be 55 ng/mL or higher.
What is biotin?
|Biotin is a B vitamin that is naturally present in a variety of foods such as eggs, beef, tuna, spinach, broccoli, milk, bananas, almonds, and more. It is estimated that the average biotin intake from foods in developed Western countries ranges from 35–70 mcg/day, which is sufficient to meet the average recommended daily value of 25–35 mcg/day for adults. It is unsurprising then, that biotin deficiency is quite rare among healthy adults.|
Why do people take biotin supplements?
|Biotin deficiencies may be seen in people who are pregnant, breastfeeding, have chronic alcoholism, or those with a rare biotinidase deficiency. Individuals in these risk groups may be recommended to take a supplemental multivitamin if neurological or cutaneous symptoms are present. In the US, newborns are also screened for a rare genetic disorder that triggers lifelong oral biotin treatment.|
Although biotin is often not necessary as a dietary supplement for the majority of people living in Western nations, a number of companies manufacture biotin supplements or multivitamins containing biotin. Many popular brands of biotin supplements contain 2,500–5,000 mcg of biotin, with some marketing large 10,000 mcg supplements. These values surpass the dietary requirements by more than 200-fold.
Measuring biotin levels in study participants
Understanding the steady state and clearance rates of biotin in serum and plasma is important as biotin supplements come in various doses. Several studies have been completed to understand the amount of serum biotin present in normal populations, as well as those taking biotin supplements. Circulating biotin levels in normal participants receiving the recommended daily dose of 30 µg have low level range of 0.1–0.8 ng/mL. Individuals consuming biotin supplements in the 2,500–5,000 mcg range have biotin concentrations ranging from 55–140 ng/mL. In extreme cases where individuals are using oral biotin doses of 10,000 mcg, blood concentrations range from 375–450 ng/mL.
Peak blood concentrations of biotin occur within one to two hours with elimination predominantly through urine. In healthy participants without impaired renal function, the elimination half-life of biotin is dependent on dosing amount and frequency. Participants taking a low dose (< 1,000 mcg) had half-life clearance rates of approximately two to three hours. Users of high dose (10,000 mcg) supplements experienced a half-life of up to nearly 19 hours.
How does biotin affect laboratory tests?
Clinical laboratories use a wide array of instruments across multiple disciplines with various testing methods. The instrument test method determines what specimen types (plasma, serum, whole blood) and tube types (heparinized, citrated, EDTA, no-additive) are appropriate. The first phase of any laboratory procedure is to consider preanalytical factors that may influence test results. One study found overall laboratory test error rates to be < 1 percent.
A number of preanalytical factors exist that influence assay analytical performance:
- Fasting status
- Sample Volume
- Clots/fibrin strands
- Transport factors
- High dose supplements
Of these factors, most are managed by laboratory staff during the preanalytical phase to prevent erroneous test results downstream.
One of the more concerning preanalytical factors are those patients taking high doses of biotin supplements. Managing biotin as a preanalytical factor is complicated by a reliance on patient compliance with instructions prior to collection.
How to mitigate biotin interference in laboratory tests
What can laboratories do to mitigate biotin interference?
Mitigating the biotin levels that can affect assay performance can take several different forms, however, some may be more difficult to accommodate than others. Replacing existing technology with new instruments isn’t always financially feasible. Likewise, using a pre-treatment step may not meet the need of some stat assays like troponin. Assay redesign is also dependent on vendor validation and FDA approval processes, which can cause significant delays to resolving issues with biotin. This leaves patient/provider education, patient pre-test instructions, test interpretive commentary, and repeat testing as the best tools to mitigate concerns around assay reliability.
What can health care providers do to mitigate biotin interference?
The importance of educating patients and providers is paramount. The FDA recommends that providers talk to their patients about any biotin or multivitamin supplements they are taking, as the supplements can affect many lab tests. Many patients expect direction from health care providers as part of preparing for a blood test, offering another opportunity for providers to discuss what foods, medications, or supplements patients should discontinue prior to the appointment. Clinical laboratories and vendors can also assist health care providers by giving them resources on assays affected by biotin interference. For example, Roche Diagnostics and Siemens Healthcare Diagnostics, who both use biotin technology, provide such handouts on their websites.
Communicating about biotin interference with patients and health care providers
Depending on the biotin dose being taken by a patient, the recommended duration to abstain from supplementation may be anywhere from two to nineteen hours. Beyond fasting status, patient pre-test instructions should include information about how the use of biotin supplements affects specific assays.
Adding interpretive comments to test results can also be used to help explain abnormality indications, recommended follow-up procedures, or reasons for a false result to health care providers. They are a great “catch all” option to guide provider decision making processes or aid in addressing test result reliability. However, they do have disadvantages. Providers can sometimes miss or ignore these comments when they are too lengthy. Further, they don’t prevent interference from occurring in the first place, and only serve as a caveat for why results may not correlate with patient clinical status.
Should test results with biotin interference be repeated?
Repeat testing is not practical in all situations but is warranted when results with a biotin affected assay are questionable. Thankfully, for assays like troponin, serial measurements are already a standard part of the operational protocol. Owing to biotin’s shorter half-life , true elevations of troponin will be detected by serial measurements when applying the recommended testing guidelines .
Avoiding erroneous patient results
Though multivitamins generally contain low levels of biotin that are unlikely to cause assay interference, biotin supplements exceeding 1 mg are of concern for some laboratory assays. While clinical labs wait for vendors to implement solutions to assays affected by biotin, clinical lab staff must use the mitigation tactics at their disposal to prevent erroneous patient results and unnecessary follow-up tests.