Can a Person Test Positive for HSV-1 Without Being Infected?
Yes, false-positive HSV-1 serologic test results can occur, though they are less common than false-negatives for HSV-1 testing. 1
Understanding HSV-1 Test Limitations
The primary issue with HSV-1 serologic testing is actually poor sensitivity rather than poor specificity—meaning false-negative results are more common than false-positives. 1
Key Test Performance Characteristics:
HSV-1 antibody assays lack sensitivity, with one study showing only 70.2% sensitivity for detecting HSV-1 antibodies, which results in frequent false-negative diagnoses rather than false-positives 1
Commercial HSV-1 IgG tests have high specificity (>97%) but low sensitivity (<85%), meaning when a test is positive, it is usually truly positive 2
The gold standard Western blot/immunoblot assay targets multiple HSV antigens and is more accurate than commercial enzyme immunoassay (EIA) or chemiluminescent immunoassay (CLIA) tests 1
When False-Positives Can Occur
While uncommon, false-positive HSV-1 results can happen in specific circumstances:
During the window period: Testing too early after exposure (within 12 weeks) may yield indeterminate or unreliable results 1
Cross-reactivity issues: Though the evidence primarily discusses HSV-2 false-positives in HSV-1 infected individuals, theoretical cross-reactivity could occur in reverse 1
Technical or handling errors: Improper specimen handling or storage can affect test accuracy 1
Clinical Reality: False-Negatives Are the Bigger Problem
The more clinically relevant issue is that 12-30% of patients with confirmed recurrent HSV-1 genital infections test falsely negative on commercial antibody assays 3. This means:
- A negative HSV-1 test does not rule out infection 3
- Multiple different antibody tests may be needed to detect HSV-1 antibodies in truly infected individuals 3
- Even patients with documented recurrent HSV-1 DNA-positive genital lesions can have persistently negative serology 3
Practical Approach to Questionable HSV-1 Results
If there is concern about a positive HSV-1 result:
- Consider the clinical context: Up to 70% of adults worldwide have HSV-1 antibodies, making true positivity common 4
- Assess for symptoms: Most HSV-1 infections are acquired during childhood through non-sexual contact and may be asymptomatic 4, 5
- Confirmatory testing is generally not needed for HSV-1 positives given the high specificity of commercial assays and high population prevalence 2
- If truly concerned, Western blot testing can be considered, though access is limited 1
Bottom Line
A positive HSV-1 serologic test almost always indicates true infection due to the high specificity of commercial assays (>97%) 2. The real diagnostic challenge with HSV-1 is the opposite problem—missing infections due to poor test sensitivity 1, 3.