HSV-2 Blood Test: Borderline, False Positive, and False Negative Explained (IgG & IgM)
Testing Methods
In current clinical practice, the primary immunoassay techniques used for quantitative antibody measurement are EIA (Enzyme Immunoassay) and ECLIA (Electrochemiluminescence Immunoassay).
FIA (Fluorescent Immunoassay) is used only in limited cases for point-of-care testing (POCT), while RIA (Radioimmunoassay) is now almost obsolete.Meanwhile, Western Blot is employed as a confirmatory test to verify the results of these immunoassays and is based on a distinct protein electrophoresis technique.
Why do test reference values differ, such as 1.0, 1.1, or 25?
Is the borderline (equivocal) result usually positive?
If clear blister symptoms are observed, or if a high index value appears within the generally recommended 8–12 weeks after possible exposure, HSV-1 or HSV-2 infection may be suspected — but it cannot be concluded with 100 % certainty.
Community and online reports show that some people remain in the borderline range for a long time, or their values slowly decline over time.
In laboratory interpretation, a borderline result does not necessarily mean it is close to positive, but rather indicates “equivocal” or “retest recommended.”
Therefore, there is no need for excessive concern; it is better to wait a little longer and get retested later.According to research, the sensitivity of HSV-2 serologic testing is high (about 92 %), meaning roughly 8 % may be false-negative. However, during the window period—the early phase right after infection before the body produces antibodies—the test can show a negative result even in infected individuals.
This window period can last up to 12 weeks, so retesting around that time is recommended.
The test characteristics are highly dependent upon the index value, with index values of 1.1–2.9 having only 39.8 % specificity, and index ≥ 3.0 having 78.6 % specificity.
Based on this, results between 1.1 and 2.9 show only 39.8 % specificity, meaning about 60 % are false positives.
Values ≥ 3.0 have around 78–80 % accuracy, while the overall average specificity is 57.4 %, which is not particularly high.
Therefore, if no clustered blisters or other clear symptoms appear, a borderline or low-positive result should not be taken as definite evidence of HSV infection.
Instead, observe for symptoms and get retested after a suitable interval.
Compared to the gold standard, there are serious limitations to the EIA/CLIA for both HSV-1 and HSV-2 testing. HSV-1 assays lack sensitivity, which can result in false-negative diagnoses. In one study, the sensitivity for detecting HSV-1 antibodies was 70.2 %.
This means that people who already carry HSV-1 are more likely to receive a false-positive HSV-2 result with low index values, due to cross-reactivity between antibodies.
What to Do After a Borderline or Positive HSV Test
If you do not have any clear symptoms, do not start antiviral medication immediately just because your result shows borderline or positive.
Instead, return to your normal routine, rest, and plan to retest after some time has passed.
There are many cases online of people experiencing severe “herpes type 2 phobia”—emotional distress despite having no clear symptoms or definitive diagnosis.
This anxiety is especially common among those who fall into the borderline (equivocal) range.
If you have been diagnosed as HSV-2 positive without visible blisters, or your result lies in the borderline range, it is advisable to avoid sexual contact temporarily for your own and your partner’s protection.
After some time, revisit your healthcare provider, discuss your previous results and any new symptoms, and take a follow-up test to confirm the diagnosis.
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