Biotin supplementation showed signs of interference with biotinylated assays in a crossover trial.

The proposed benefits of biotin (vitamin B7), including stimulating hair growth and assisting in the treatment of various forms of diabetes, have made it a popular supplement. Supplementation generally leads to artificially high levels of biotin, which was shown to cause inaccurate results in biotinylated assays, according to Danni Li, PhD, of the advanced research and diagnostic laboratory at the University of Minnesota, Minneapolis, and her colleagues.

They analyzed the results of both biotinylated and nonbiotinylated assays of six patients – two women and four men – who ingested 10 mg/day of biotin supplement for 7 days. Two blood samples were obtained in the course of the study: one prior to starting biotin supplementation as a baseline and one a week ofter biotin supplementation had ended. The assays tested the presence of nine hormones and two nonhormones using multiple diagnostic systems to run the assays. In total, 37 immunoassays were conducted on each sample (JAMA. 2017;318[12]:1150-60. doi: 10.1001/jama.2017.13705).

Two immunoassay testing techniques were used in the diagnostic assays. The sandwich technique was used in testing TSH, parathyroid hormone (PTH), prolactin, N-terminal pro-brain natriuretic peptide (NT-proBNP), PSA, and ferritin and competitive technique was used in testing total T4, total T3, free T4, free T3, and 25-OHD. In assays utilizing competitive techniques, false highs were reported in three Roche cobas e602 machines and one Siemens Vista Dimension 1500 machine.

Assays utilizing the sandwich technique experienced false decreases in TSH, PTH, and NT-proBNP when compared with baseline measurements in Roche cobas e602 and OCD Vitros 5600 machines. A predominance of the falsely low results were present in the assays conducted by the OCD Vitros machine, with significant changes from baseline measurements. TSH experienced a 94% decrease of 1.67 mIU/L, PTH experienced a 61% decrease of 25.8 pg/mL, and NT-proBNP falsely decreased by more than 13.9 pg/mL. In Roche cobas e602 assays, TSH levels were falsely low and measurements decreased by 0.72 mIU/L (37%) when compared with baseline measurements.

Biotin did not interfere in all biotinylated assays and was only observed in 9 of the 23 (39%) of the assays conducted. Specifically, 4 of 15 (27%) sandwich immunoassays were falsely decreased while five of eight (63%) competitive binding assays were falsely increased.

“Among the 23 biotinylated assays studied, biotin interference was of greatest clinical significance in the OCD Vitros TSH assay, where falsely decreased TSH concentrations (to less than 0.15 mU/L) could have resulted in misdiagnosis of thyrotoxicosis in otherwise euthyroid individuals,” according to Dr. Li and her associates, “Likewise, falsely decreased OCD Vitros NT-proBNP, to lower than assay detection limits, could possibly result in failure to identify congestive heart failure.”

One investigator received funding and nonfinanical support from Siemens Healthcare Diagnostics, one reported receiving financial support from Abbott Laboratories, and another reported receiving personal fees from Roche and Abbott Laboratories. Dr. Li and the other researchers had no relevant financial disclosures.


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