Which factor can cause a false positive blood bhCG result?

• A. Aspirin
• B. Proteins
• C. Urinary drug metabolites
• D. Hemoglobin

Answer: (A)

Immunoassay tests for hCG can be fooled by substances that cause non-specific antibody binding or otherwise alter the assay environment, leading to a signal even when hCG isn’t present. Aspirin can do this in some blood hCG tests by changing how the antibodies interact or by affecting the sample matrix, so a color development appears as a positive result without actual hCG. In practice, this means a patient taking aspirin could yield a falsely positive pregnancy test in certain assay configurations, which is why this factor is highlighted as a potential interference.