Thyroid Assay- Biotin Interference

 

By Pradeep K. Bhagat, MD, System Chairman, Department of Pathology,

All Main Line Health Laboratories are utilizing Beckman Coulter instrument for measurements of T4, T3, Free T4, Thyroglobulin antibody and Thyroglobulin. We have been notified by Beckman Coulter that high level of biotin can cause interference with free T4, Thyroglobulin and total T3.  Beckman Access immunoassays use biotin-coupling or biotin-streptavidin chemistry in their assay design.

Biotin is a water soluble vitamin that is easily cleared in a fasting patient. Beckman Coulter performed interference testing with two concentrations of biotin 7.5 ng/ml (three times the normal healthy human serum concentration) and 100 ng/mL (the maximum expected concentration in human serum).  The samples spiked with 7.5 mg/ml did not demonstrate interference; however, biotin concentration at 100 ng/mL cause interference with free T4, total T3 and thyroglobulin. Total T3 and free T4 are expected to give higher results in patients taking biotin, whereas thyroglobulin will be lower in patients taking biotin.

Our recommendation is to use clinical correlation. If a patient is taking biotin vitamins and is going to get blood drawn for thyroid testing, patient should be fasting and should skip biotin before blood draw.

As always, please do not hesitate to call Dr. Bhagat, Medical Director of Main Line Health

Laboratories at 484-476-3521 with any questions.

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