Serum biotin interference: A troublemaker in hormone immunoassays.

Objectives: Biotin therapy can affect the results of many immunoassay procedures. The present study investigates biotin's interference on 25-hydroxy vitamin D (25-OHD), parathyroidhormone (PTH) and thyroid-stimulating hormone (TSH) tests using four different assay systems and biotin neutralization.

Design And Methods: Enrolled in the study were 50 children diagnosed with biotinidase deficiency (BTD) undergoing treatment with biotin (5-20 mg/day) who were subjected to a series of analyses involving 25-OHD (Roche Diagnostics assays, Beckman Coulter assays, HPLC, LC/MS-MS), TSH, PTH (Roche Diagnostics assays, Beckman Coulter assays) and biotin (LC/MS-MS), before and after biotin neutralization with Streptavidin-coated magnetic particles (SMP).

Results: The median biotin concentration was found to be 175.2 [94.0-307.1] μg/L. There was no significant difference in the 25-OHD results before and after neutralization with the Beckman Coulter, HPLC and LC-MS/MS assays. In contrast, the median 25-OHD level was seen to decrease from 90.2 [35.9-105.3] ng/mL to 29.1 [22.6-37.6] ng/mL after neutralization with the Roche assay (p < 0.0001). While there was no statistically significant difference in the values recorded before and after neutralization in PTH analysis using Beckman assay, the median PTH levels increased from 7.8 [1.6-21.6] pg/mL to 28.2 [22.5-41.9] pg/mL after neutralization with the Roche assay (p < 0.0001). The cut-off values at which serum biotin interfered in the Roche assay PTH test, with 25-OHD levels determined as 51.4 μg/L and 62.9 μg/L, respectively. A significant increase was detected in the TSH levels analyzed with a Roche assay after neutralization (from 2.36 [1.85-3.00] mIU/L to 2.74 [1.93-3.70] mIU/L, p < 0.0001).

Conclusions: The PTH, 25-OHD and TSH results were found to be affected by high biotin concentrations in Roche assays, leading to a risk of misdiagnosis, although SMP neutralization can suppress any such interference efficiently.