LAUSR

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 51.4μg/L and 62.9μg/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.