To the Editor:

Kummer and colleagues draw timely attention to the serious problem of biotin interference in thyroid-function tests. As they report, biotin plays an important role in the treatment of patients with rare inborn errors of metabolism. Recently, however, high-dose biotin has been adopted in the treatment of multiple sclerosis and this has led to a succession of false diagnoses of thyrotoxicosis in patients with multiple sclerosis.

Biotin interference is not limited to thyroid-function tests. Streptavidin–biotin is used extensively by laboratories to improve the sensitivity of many immunoassays. Biotin interfered with thyroid-function tests and other tests of serum obtained from a patient with multiple sclerosis who had received a single dose of 300 mg of biotin several hours before the blood sample was obtained. Biotin Interference with Streptavidin–Biotin Immunoassays Leading to Falsely High Results in Competitive Formats and Falsely Low Results in Sandwich Formats.). Biotin interference caused falsely high results in tests that involved the use of streptavidin–biotin in a competitive immunoassay format and falsely low results in tests in which this technique was applied in a sandwich immunoassay format.

It is crucial that clinicians be aware of this interference. In patients who are receiving high-dose biotin, this agent should be withheld for 72 hours before blood tests in order to minimize interference.

Christina M. Trambas, M.D., Ph.D.
Ken A. Sikaris, M.D.
Zhong X. Lu, M.D., Ph.D.
Melbourne Pathology, Collingwood, VIC, Australia

As Trambas and colleagues note, the problem of biotin-induced laboratory errors is not limited only to tests in patients with inherited metabolic diseases. The spectrum of potentially affected persons is broad and ranges from those with multiple sclerosis to those with alopecia, onychorrhexis, dermatitis, diabetes mellitus, or depression. Patients with these conditions have been reported to potentially benefit from biotin treatment, and patients often use biotin that is available over the counter as a complementary medicine.

Moreover, apart from thyroid-function tests, numerous other critical laboratory values such as those of tumor markers, many hormones, and vitamins, as well as markers used in the diagnosis of infectious diseases, are measured with the use of streptavidin–biotin methods. Therefore, every clinician should be aware of biotin-interfering assays used in his or her laboratory examinations, and patients should be asked about biotin intake. In turn, clinical laboratories should indicate potential biotin interference whenever possible and keep alternative laboratory methods in mind. Finally, the problems discussed here may also stimulate the efforts of manufacturers of laboratory kits to minimize biotin interference (e.g., by taking steps to block or eliminate biotin from the blood sample before the use of the immunoassay).

Sebastian Kummer, M.D.
Derik Hermsen, M.D.
Felix Distelmaier, M.D.
Heinrich Heine University Hospital, Düsseldorf, Germany