Falsely Elevated 25-Hydroxyvitamin D Level Due to High Dose Biotin Supplement in a Patient with Multiple Sclerosis

Presentation Number: LB MON 46
Date of Presentation: April 3rd, 2017

Katherine Gheysens*1 and Sara E Lubitz2
1Rutgers Robert Wood Johnson Medical School, 2Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ

Abstract

Introduction: Biotin supplement (vitamin B7) intake interferes with hormone testing when streptavidin-biotin-based immunoassays are used. This may lead to falsely elevated or low hormone levels and consequently, misdiagnosis of patients. There are previously published cases of biotin interfering with competitive or immunometric hormone assays, however, this interference has not yet been reported in 25-hydroxyvitamin D (25(OH)-D) testing.

Clinical Case: A 58-year old female with progressive multiple sclerosis on interferon beta-1b therapy presented for evaluation of an extremely elevated 25(OH)-D level. She showed no symptoms of hypervitaminosis D or hypercalcemia. Additionally, the patient had no history of vitamin D or calcium abnormalities. Testing eight months prior showed normal levels of 25(OH)-D 38.8 ng/mL (nl 25-80), Ca 9.7 mg/dL (nl 8.5-10.2) and Cr 0.6 mg/dL (nl 0.5-1.6). Five months prior to presentation the patient was noted to have elevated 25(OH)-D >180 ng/mL. At that time the patient discontinued all Vitamin D supplementation as advised by the ordering physician. Repeat testing obtained three months later, again demonstrated an elevated level of 25(OH)-D >180 ng/mL.

On Endocrinology evaluation, it was noted that the patient was taking 300mg of biotin daily, prescribed by her neurologist for multiple sclerosis therapy. Suspecting interference of the biotin with the 25(OH)-D testing, it was confirmed with the laboratory that the immunoassay used was streptavidin-biotin-based. The patient was advised to temporarily discontinue the biotin for 5 days. Repeat testing demonstrated normal levels of 25(OH)-D 37.0 ng/mL, Ca 9.7 mg/dL, and PTH 38 pg/mL (nl 9-76). This confirmed the patient’s elevated 25(OH)-D level was due to laboratory error. She was instructed to resume biotin supplementation, and to hold it prior to any future hormone testing.

Conclusion: With addition of high-dose biotin to therapy protocols for multiple sclerosis and its recent popularity from claims of improving hair, skin and nails, there has been increasing awareness about biotin interference with thyroid hormone testing (1).This is the first case demonstrating that biotin intake can also interfere with and falsely elevate 25(OH)-D laboratory results when a streptavidin-biotin-based immunoassay is used. It is imperative that more attention be brought to biotin interference to avoid false laboratory results and potential misdiagnosis of patients.

 

Nothing to Disclose: KG, SEL