Biotin (Vitamin B7) supplementation, particularly at high doses (≥5 mg/day), has been increasingly recognized as a significant source of interference in biotin-streptavidin-based immunoassays (such as ECLIA, ECL), potentially leading to misinterpretation of critical laboratory results. This interference arises from biotin’s strong binding to streptavidin reagents used in many modern immunoassays, disrupting the assay signal (See Table 1).

PHARMACOKINETICS OF BIOTIN:

Biotin is rapidly absorbed after oral administration, reaching peak plasma concentrations within 1-2 hours post-ingestion. The elimination half-life varies significantly based on dosage:

Low doses (≤10 mg): Half-life of approximately 2 hours.

High doses (≥100 mg): Half-life extends up to 18.8 hours.
Biotin exhibits dose-dependent accumulation, with steady-state concentrations achieved after 3 days of consistent dosing. Renal impairment can substantially prolong elimination, necessitating extended washout periods.

Critical Timing Considerations Based on Dosage:

Over-the-Counter Multivitamins (≤1 mg/day):

No significant interference reported.

No special timing requirements.

2. Moderate-Dose Supplements (5-10 mg/day):

• Peak concentrations: 55-140 ng/mL at 1-2 hours post-dose.
• Wait time: ≥8 hours after last dose before blood collection.
• Example: If taken at 8 AM, schedule blood draw after 4 PM.

3. High-Dose Biotin Therapy (100-300 mg/day):

• Peak concentrations: 375-450 ng/mL at 1-2 hours post-dose.
• Wait time: Minimum 72 hours (3 days) after last dose.
• Critical for MS patients and metabolic disorder treatments.

4. Very High-Dose Regimens (>300 mg/day):

• May require washout periods up to 5-7 days.
• Consider biotin level testing before critical assays.

REFERENCES:

Based on AACC Guidance Document and manufacturer recommendations (2020)

AUTHORS:

Mohsen Rokni, PhD, Laboratory Technical Manager

Department of Immunology, Email: Mohsenrokni1@yahoo.com

Keyvan Majidi, Supervisor

Noor pathobiology and genetic lab supervisor, Email: keyvan_majidi@yahoo.com

Table 1. Interference thresholds for biotin-mediated interference as obtained from manufacturers’ assay package inserts

– Data are not all inclusive and do not contain information on all laboratory tests.

– The data are presented as reported by individual manufacturers at the time of this providing.

– To convert ng/mL to nmol/L, multiply ng/mL by 4.093.