Recently the consumption of biotin (vitamin B7, component of multivitamins and of hair and nail products, medication for Multiple Sclerosis) has increased and as result the following interfering patterns have been observed:
increased FT4 and decreased TSH mimicking Graves disease or hyperthyroidism;
decreased PTH with increased vitamin D mimicking PTH suppression or vitamin D intoxication;
increased cortisol with decreased ACTH mimicking hypercortisolism (1)
Because some immunoassays will show falsely decreased (TSH, CA 125, prolactin, F-PSA, NT-PBNP) while others falsely increased values (T3, FT4, cortisol, estradiol, folate) some interference combinations can mimic certain disease states that will not match the clinical picture, and consultation with the laboratory is recommended. T-messages explaining the possible interference will be attached to the results that could be affected.
Risk to Patient:
Although present in literature these interferences are rare: the patients at the highest risk of misdiagnosis are
consumers of high dose of biotin (Multiple Sclerosis, or oncology patients 100,000 mcg/day)
patients who take increased amounts of pure biotin or beauty products (5,000 to 10,000 mcg/tablet),
patients who take biotin in an moderate amount but have kidney failure who having a delayed clearance of the vitamin.
Biotin, vitamin B7 or vitamin H is a water-soluble vitamin eliminated through the kidney with a half-life between 8 and 24 hours, variable from person to person and increased with kidney failure. Because biotin deficiency is considered extremely rare, no RDI exists. Suggested biotin intake for adults ranges from 30 – 100 mcg per day. Standard multivitamins contain usually 30-50 mcg/tablet, amount will not interfere with our testing, while the beauty products and the MS medication might produce interference.
We recommend asking the patient if he/she is taking treatment, multivitamins or beauty products containing biotin.
A 12 hour abstinence would ensure the clearance of biotin to a level that would not interfere with our results if the patient takes regular multivitamins or beauty supplements.
For patients taking doses exceeding 5,000 mcg/day (usually MS treatment) a longer period of abstinence as well as consultation with the laboratory is recommended.
The laboratory is able to identify biotin or any other interferences, communication with the laboratory is recommended whenever the results are discrepant with the clinical picture.
Clinical chemistry testing (electrolytes, glucose, creatinine, lipids, liver enzymes) based mainly on chemical and enzymatic reactions and immunoassays performed on ELISA platforms like lyme, measles, autoimmune assays, or urine pregnancy tests are not affected by biotin but can be influenced by other interferences.
Our immunoassays are very accurate and reliable but various interferences are possible and a complete list of medication, accurate clinical history as well as a good correlation between the clinical picture and the laboratory results is imperative for patient care.
The laboratory has methods to identify possible interferences and we are at your service to discuss and follow up on any results that do not have a good clinical explanation, as well as to listen to any questions or suggestions that you might have.
Please see below some examples of different patterns of thyroid function results and their possible causes.
1.Piketty ML, Polak M et al: False biochemical diagnosis of hyperthyroidism in streptavidin-biotin-based immunoassays: the problem of biotin intake and related interferences. Clin Chem Lab Med 2017; 55 (6): 780-788
2. Koulouri O, Moran C et al: Pitfalls in the measurement and interpretation of thyroid function tests. Best practice & Research Clinical Endocrinology & Metabolism 27 (2013): 745-762