Our experts respond to a very timely concern about the evident interference of biotin in laboratory testings.1
Biotin, also known as B7, or water-soluble vitamin H, is a cofactor in enzymatic carboxylation reactions of fatty acid and branched chain amino acid metabolism, gluconeogenesis, and the Kreb’s cycle.2,3 While the recommended daily intake of biotin is 30 mcg for adults, the average intake of this micronutrient in Western diets is about 35-70 mcg daily.4
Approximately 15-20% of US adults take supraphysiologic doses of biotin-containing supplements for common hair and skin problems, weight loss, enhanced glucose metabolism, and to boost energy.4 Biotin also has pharmacologic indications for multiple sclerosis, malabsorption syndrome, dysregulation of mitochondrial energy metabolism, biotin-thiamin responsive basal ganglia disease, and genetic biotin deficiency.5 It is also used in alleviating muscle cramps in hemodialysis patients.
Unfortunately, when consumed in high doses typically found in over the counter supplements, biotin interferes with the biotin-streptavidin system used in many immunoassays.2 The biotin-streptavidin complex is reliable for its strong non-covalent bond. The strong affinity of biotin to streptavidin makes it resistant to organic solvents, denaturants, detergents, proteolytic enzymes, as well as extremes of temperature and pH.
An excess biotin intake may adversely effect immunoassays in two different ways:
For a list of common endocrine-related competitive and sandwich assays that may return inaccurate findings in the presence of biotin supplementation see Table 1.
There are many erroneous biochemical diagnoses that may occur in patients taking high dosages of supplemental biotin.
Imagine, for example, a case in which lab results on a patient indicate elevated free thyroxine, elevated free triiodothyronine, elevated TSH receptor antibodies as well as a low TSH. A clinician would view this constellation of findings as indicative of possible Graves’ disease.
Alternatively, the same constellation of laboratory findings may be obtained for a euthyroid patient taking excessive biotin. Similarly, the laboratory findings for patients treated with testosterone replacement may show a false low or normal PSA levels in the presence of excess biotin supplementation.
Likewise, primary hyperparathyroidism would be difficult to diagnose in patients with hypercalcemia and falsely low PTH. It is of utmost importance to obtain a comprehensive history of biotin use when conducting an initial intake of all medications taken, and again before bloods are drawn to assess endocrine hormone levels to avoid the potential for misdiagnosing a patient without assurance that biotin is not a contributory factor to the results.
Clinicians are cautioned to act decisively given the risk of inaccurate or missed diagnosis and in light of the urgency that prompted a Food and Drug Administration (FDA) Safety Communication on this very topic.
The FDA recommends1 that clinicians take the following precautions:
The FDA reports taking the following actions—working with stakeholders to better understand biotin interference with laboratory tests in order to develop recommendations for more accurate testing in patients who have taken high levels of biotin in advance of laboratory testing.1
For specific directives in the FDA Safety Communication, go to: FDA.