How does biotin interfere with laboratory tests?

How Biotin Interferes with Laboratory Tests

Biotin interferes with laboratory immunoassays that use streptavidin-biotin binding chemistry, causing falsely elevated results in competitive assays and falsely decreased results in sandwich (noncompetitive) assays, with the direction and magnitude of interference varying by specific test and manufacturer. 1

Mechanism of Interference

Biotin from over-the-counter dietary supplements interferes with biotin-streptavidin based immunoassays through competitive binding mechanisms 1:

• In competitive assays: Excess biotin causes false-positive (falsely elevated) results by competing with biotinylated reagents 1, 2
• In sandwich assays: Excess biotin causes false-negative (falsely decreased) results by blocking streptavidin binding sites 1, 2

The interference occurs because many modern immunoassays use biotinylated antibodies/antigens paired with streptavidin for detection, and exogenous biotin in patient samples competes with these assay components 2.

Clinically Significant Affected Tests

Cardiac Markers

• Troponin assays are particularly vulnerable to biotin interference, which can result in falsely low troponin levels and potentially missed myocardial infarctions 1, 3
• This represents a critical patient safety concern in emergency cardiac evaluations 1

Endocrine Tests

• Thyroid function tests (TSH, free T4, free T3) show significant interference 2, 4
• Aldosterone and renin: Aldosterone shows massive positive interference (up to +3484% bias), while renin shows severe negative interference (up to -98% bias) at biotin concentrations of 100-500 ng/mL 5
• Growth hormone and IGF-1: Significant bias (>10%) occurs at biotin concentrations ≥100 ng/mL 5

Other Affected Tests

• Hormone assays including β-hCG 2
• Cancer markers 2
• Drug level monitoring 2
• HIV antigen-antibody combo assays: HIV-1 p24 antigen becomes undetectable at biotin concentrations ≥200 ng/mL 6
• Bone alkaline phosphatase: Significant interference at biotin ≥500 ng/mL 5

Biotin Concentrations and Clinical Context

Normal vs. Supplemental Intake

• Normal dietary biotin intake from foods and milk does not cause interference in immunoassays 2
• High-dose supplementation (100-300 mg daily) poses significant problems for streptavidin-biotin based assays 2
• Interference thresholds vary significantly by test and cannot be easily predicted 2

High-Risk Patient Populations

Patients taking high-dose biotin supplements include those with 2, 4:

• Multiple sclerosis (often 300 mg daily)
• Biotinidase deficiency
• Mitochondrial metabolic disorders
• Cosmetic purposes (hair, skin, nail improvement)

Laboratory Detection and Management Strategies

Identifying Biotin Interference

Laboratories should suspect biotin interference when 4:

• Results are discordant with clinical presentation
• Multiple test abnormalities occur in patterns consistent with biotin interference
• Patient reports taking biotin supplements

Biotin Removal Methods

The validated solution is streptavidin-coated microparticle depletion 7:

• Uses the same streptavidin-coated magnetic microparticles that are components of susceptible assays
• Successfully depletes high biotin concentrations from serum
• Restores normal results in samples from multiple sclerosis patients taking 300 mg biotin daily
• Applicable to both competitive and sandwich immunoassays
• Does not significantly change measurement precision or accuracy for most analytes 7

Timing Considerations

For planned testing, patients should discontinue biotin supplementation for >48 hours before blood draw 2, 4:

• Biotin has a relatively short half-life in the human body
• This allows rapid elimination and follow-up specimen analysis if necessary 4
• Critical caveat: This approach is not feasible for emergency situations or patients with biotinidase deficiency who require continuous biotin therapy 2

Manufacturer and Laboratory Responsibilities

Immunoassay manufacturers must investigate biotin interference up to at least 1200 ng/mL (4.9 μM) in their assays 2:

• Interference thresholds vary significantly between manufacturers and test formats 4
• Laboratories should be aware of specific biotin tolerance levels for their assays 4

Laboratories should implement protocols for 4:

• Screening for biotin use in patient history
• Confirming suspected interference through biotin depletion or repeat testing after supplement discontinuation
• Communicating with clinicians about potential biotin interference

Critical Clinical Pitfalls

The most dangerous scenario is falsely low cardiac troponin in patients with acute coronary syndrome 1:

• Can lead to missed myocardial infarction diagnosis
• Represents a life-threatening misdiagnosis
• Emergency department physicians must be aware of this interference pattern

There is currently no rapid, reliable procedure for detecting biotin at nanomolar levels in blood samples 2:

• Traditional HPLC/MS-MS cannot process large numbers of samples quickly
• This represents a significant gap in clinical laboratory capabilities 2