Gantt K, Muthukumar A. Systematic analysis of biotin interference in Roche chemistry assay. Am J Clin Pathol. 2018;149 (Suppl 1):S7-S12.
To assess whether biotin supplements cause interference in routine clinical laboratory testing, including thyroid-stimulating hormone (TSH), free triiodothyronine (T3), free thyroxine (T4), parathyroid hormone (PTH), troponin-T, and N-terminal pro–B-type natriuretic peptide (NTproBNP).
Design and Participants
Three adult volunteers (2 women and 1 man) were administered either 1 mg, 5 mg, or 10 mg of USP-grade biotin supplement per day. Each participant took the given dose for 5 days, starting with the lowest dose. Blood samples were collected at baseline and following completion of each 5-day dose intervention.
Two serum pools were made for each analyte (TSH, free T3, free T4, human chorionic gonadotropin [hCG], PTH, troponin-T, and NTproBNP). Aliquots from each pool were spiked with 1, 5, 10, 50, 100, 500, 1000, and 10,000 ng/mL of biotin to determine the extent of biotin interference in each assay tested.
None of the doses of biotin in any of the Roche assays tested had any interference in the 3 volunteers taking up to 10,000 mcg (10 mg) biotin. All of the analytes in the serum pools were tested for interference. At biotin concentrations up to 10 ng/mL, no interference occurred in the free T3 and free T4 assays, while for the TSH assay no interference was observed up to 5 ng/mL. Higher biotin concentrations resulted in significant interference. The hCG, PTH, and NTproBNP assays experienced some degree of interference starting at 1 ng/mL, reaching very significant interference above 5 ng/mL. No interference was observed in the troponin-T assay up to a biotin concentration of 100 ng/mL.
According to the current Dietary Reference Intakes (DRIs) established by the Food and Nutrition Board of the National Academies of Sciences, Engineering, and Medicine, the Adequate Intake (AI) of biotin is 35 mcg for lactating women, 30 mcg per day for adult men and women, including pregnant women, and 5 to 20 mcg for children.1 Since the AI for biotin was suggested in 1998,2 a growing body of literature has suggested a wider range of potential benefits for biotin beyond its estimated physiological requirements. Acceptable use of high-dose therapeutic treatment has included those with autosomal recessive disorders such as biotinidase and holocarboxylase deficiencies or propionic acidemia.3-8 However, there may be other therapeutic uses of high-dose biotin.
Also known as vitamin B7, this water-soluble B-vitamin has been administered orally without toxic effects at doses as high as 5 mg per day for children with uncombable hair syndrome,9 25 mg per day for children with developmental delay-autism spectrum disorder,10 and 300 mg per day (10,000 times the AI for biotin) for up to 3 years for adults with secondary progressive multiple sclerosis.11-13
It has recently been reported that biotin supplementation may interfere with laboratory assays, including immunoassays for small molecules such as free T4, free T3, cortisol, estradiol, and testosterone, resulting in either falsely high or falsely low values across several immunoassay platforms (Roche Cobas e602; Siemens Centaur; Siemens Dimension Vista).14,15 Whether there is interference or not may depend on the type of assay used. In one study of thyroid panel assays with biotinylated components (molecules with biotin attached to them), higher levels of biotin falsely increased results with competitive free T3, free T4, total T4, and total T3 assays, and decreased results with the sandwich TSH assays.8 Thus, biotin can cause interference in such assays that incorporate biotinylated components. This is clinically relevant for patients who are taking biotin supplements when they undergo thyroid panel testing and can result in possibly confusing or misleading results.
Recently, Lam and colleagues reported hyperthyroidism diagnosed due to biotin-like assay interference in patients not taking biotin supplements. This occurred in a 77-year-old female patient whose thyroid function test was suggestive of hypothyroidism, as well as in a 25-year-old female prescribed carbimazole for apparent primary hyperthyroidism. In both cases, an approximately 100 kDa immunoglobulin M (IgM) with high affinity to streptavidin isolated from each patient’s serum was related to IgM anti-streptavidin antibodies causing analytical interference. Initially biotin had been falsely attributed as the cause of analytical interference, but neither patient had been taking biotin-containing supplements.16
That biotin supplementation might affect the performance of hormone and nonhormone assays in healthy adults received widespread attention in 2017, following publication of an article in JAMA that reported results of a nonrandomized crossover study of 6 healthy adults taking 10 mg biotin per day for 1 week.17 Not long afterwards, the US Food and Drug Administration (FDA) issued a safety communication, cautioning that biotin supplementation may interfere with lab tests and cause incorrect test results that go undetected.18 The agency’s safety alert included a report that 1 patient taking high levels of biotin died following falsely low troponin test results when a troponin test known to have biotin interference was used. It was for this reason that detailed Roche immunoassays were conducted to address clinician concerns. This present study by Gantt and Muthukumar found that biotin concentrations up to 100 ng/mL did not interfere with the troponin-T assay, which raises the question: Can the death reported by the FDA be attributed to biotin supplementation without knowing what assay panel was used, what biotin dose was consumed, or whether the individual had biotin levels above physiological levels?
As some 20 states now allow consumers to have serum/blood tests performed without a physician referral, the FDA urges laboratories to communicate with individuals submitting a sample if they are taking supplements containing biotin.
Healthcare providers should talk to patients who may be supplementing with high doses of biotin for conditions such as brittle nails19 or other cutaneous indications20 about the potential interactions between biotin and lab assays. Providers should encourage these patients to quit taking biotin 2 to 4 days prior to lab testing. Grimsey and colleagues report that to avoid the risk of false assay results, an 8-hour washout period is sufficient following biotin intake at dose regimens of 1 mg to 300 mg q.i.d.; for daily doses ≥10 mg, a washout period of up to 73 hours may be necessary.21
As some 20 states now allow consumers to have serum/blood tests performed without a physician referral, the FDA urges laboratories to communicate with individuals submitting a sample if they are taking supplements containing biotin. According to the FDA, supplements containing biotin at 0.03 mg (30 mcg) do not typically cause significant interference.11 However, for patients who are taking high-dose biotin supplements there may be interference with laboratory testing, depending on the assay used.
It is interesting that the issue of lab interference has not come up sooner, since a number of foods are quite rich in biotin (though many of these foods are not common in the American diet). Some examples of the most biotin-rich foods are listed in the table below. Fruits and vegetables provide negligible or undetectable amounts of biotin.22
Table. Biotin-rich Foodsa
|Food||Biotin (mcg/100 g)|
|Raw chicken liver||210|
|Dried baker's yeast||200|
|Fried chicken liver||170|
|Raw egg yolk||60|
|Compressed baker's yeast||60|
|Fried calf liver||59|
|Stewed ox liver||50|
|Raw ox kidney||49|
|Fried lamb liver||41|
|Raw lamb liver||37|
|Stewed pig liver||34|
|Raw pig kidney||32|
|Raw pig liver||27|
|Fried cod roe||15|
|Raw cod roe||13|
a Source: McCance R. McCance and Widdowsons’ The Composition of Foods. 4th ed. London, England: Elsevier; 1974.14
Because the biotin content of foods comes from McCance and Widdowson’s reference book on food composition, the values may not be reliable—the food chemists who contributed to this book used an archaic microbiological assay. Currently, the United States Department of Agriculture (USDA) is using a high-performance liquid chromatography (HPLC) method for biotin assessment in foodstuffs. However, the results have not been made public. Nevertheless, a scattering of literature confirms that the kinds of foods shown above are indeed rich in biotin.