Which blood tests does Nutrafol (biotin supplement) interfere with?

Nutrafol (Biotin) Interference with Blood Tests

Nutrafol, which contains biotin, primarily interferes with streptavidin-biotin-based immunoassays, most notably causing false results in cardiac troponin tests, thyroid function tests (TSH, fT3, fT4), and other hormone assays. 1, 2, 3

Key Blood Tests Affected by Biotin Interference

Cardiac Biomarkers

• Cardiac Troponin T (high-sensitivity): False-negative results can occur with biotin supplementation, potentially missing myocardial infarction 1, 4
• Other cardiac markers: Tests using biotin-streptavidin technology may be affected

Thyroid Function Tests

• Thyroid Stimulating Hormone (TSH): Falsely lowered results 3
• Free T4 (fT4): Falsely elevated results 3
• Total T3 (TT3): Falsely elevated results 3
• Thyroglobulin (Tg): Falsely lowered results 3

Other Hormone Tests

• Prostate Specific Antigen (PSA): Potential for interference 5
• Various other hormone assays: Any using streptavidin-biotin technology 2

Mechanism of Interference

Biotin interference occurs due to:

• Assay design: Depends on whether the test uses a competitive or sandwich immunoassay method 1
• In competitive assays: Biotin causes falsely elevated results
• In sandwich assays: Biotin causes falsely decreased results

Factors Affecting Interference Severity

1. Biotin dose: Higher doses create greater interference
2. Time since last biotin ingestion: Maximum interference occurs approximately 2 hours after biotin intake 3
3. Assay platform: Different manufacturers have varying susceptibility to biotin interference
   • Roche Cobas platforms are particularly susceptible 3, 4
   • Abbott Architect platforms show less interference 3
   • Siemens IMMULITE platforms show interference with certain tests 3

Clinical Implications

• Cardiac testing: False-negative troponin results could lead to missed diagnosis of myocardial infarction 1, 4
• Thyroid testing: Pattern of falsely low TSH with falsely high T4 can mimic hyperthyroidism 3
• Cancer monitoring: False-negative tumor markers could affect cancer surveillance 3

Recommendations for Clinicians

1. Ask about supplement use: Specifically inquire about Nutrafol, biotin supplements, or multivitamins containing biotin
2. Timing of blood draws: If possible, instruct patients to stop biotin supplementation:
   • At least 8 hours before blood draws for standard doses (≤5 mg/day)
   • At least 72 hours before blood draws for high doses (>5 mg/day)
3. Consider alternative assays: When biotin interference is suspected, use:
   • Mass spectrometry-based methods which are not affected by biotin 3
   • Newer generation immunoassays designed to be less susceptible to biotin interference 4
   • Alternative assay platforms with different detection methods

Prevalence and Risk Assessment

• Risk of clinically significant interference varies by population:
  • UK study found extremely low prevalence of biotin levels high enough to cause interference 6
  • US studies show higher prevalence (7.4%) of potentially interfering biotin levels 5
• Nutrafol contains biotin at doses that could potentially cause interference, especially if taken shortly before blood testing

Important Caveats

• Newer assay generations: Some manufacturers have developed updated assays with higher tolerance to biotin interference (up to 1200 ng/mL) 4
• Laboratory notification: Always inform the laboratory when a patient is taking biotin supplements
• Unexpected results: Consider biotin interference when laboratory results don't match clinical presentation

Remember that biotin interference is dose and time-dependent, with maximum interference typically occurring 2 hours after ingestion and diminishing over time as biotin is cleared from circulation.