QUICK ANSWER
The HSV-2 IgG test measures herpes simplex virus type 2 antibodies in the blood. The result is reported as an index value — a number that falls in one of three zones.
| Index value | Zone | What it means |
|---|---|---|
| Below 0.90 | Negative | No HSV-2 antibodies detected above threshold |
| 0.90–1.09 | Equivocal | Borderline — repeat testing in 12 weeks recommended |
| 1.10 and above | Positive | HSV-2 antibodies detected — past exposure indicated |
Important caveat: A positive result in the 1.10–3.5 range has a significant false positive rate. Confirmatory testing is recommended before a diagnosis is made.
Common questions at a glance:
| Question | Short answer |
|---|---|
| What does "reactive/abnormal" mean? | "Reactive" and "abnormal" are lab report terms for a positive result — the index value is above the threshold |
| What does equivocal mean? | Borderline result (0.90–1.09) — the test cannot confirm positive or negative; repeat in 12 weeks |
| What does a high index value mean? | A higher index value generally indicates a stronger antibody signal, but the number itself doesn't determine severity of infection |
| Can the test give a false positive? | Yes — false positives are common in the 1.10–3.5 range; confirmatory testing is recommended |
| What is the reflex inhibition test? | A second test automatically run when the initial index is 1.10–6.00 to confirm whether the initial positive is true or false |
| I tested positive but have no symptoms — is this normal? | Yes — most HSV-2 infections are asymptomatic or unrecognized; a positive IgG means past exposure, not necessarily active disease |
UNDERSTANDING YOUR HSV-2 INDEX VALUE — THE COMPLETE RANGE TABLE
The HSV-2 IgG test on the HerpeSelect ELISA (used by LabCorp and other major labs) reports results as an index value. Here is how to read the full range:
| Index value | Zone | Interpretation | Recommended action |
|---|---|---|---|
| <0.90 | Negative | No significant HSV-2 antibodies detected | No action needed; if recent exposure (<16 weeks), repeat testing to allow window period to close |
| 0.90–1.09 | Equivocal | Borderline — cannot confirm positive or negative | Repeat testing in 12 weeks with same platform |
| 1.10–1.99 | Low positive | Above threshold — confirmatory testing strongly recommended before diagnosis | HSV-2 IgG inhibition assay or Western blot |
| 2.00–3.49 | Low-moderate positive | Still in elevated false positive zone — confirmatory testing recommended | HSV-2 IgG inhibition assay or Western blot |
| 3.50–5.99 | Moderate positive | Lower false positive risk — inhibition reflex often still performed | Clinical correlation; inhibition assay if available |
| 6.00–23.99 | High positive | Well above threshold — true positive very likely | Clinical evaluation; partner notification discussion |
| ≥24 (or ">23") | Very high positive | Markedly elevated — strong evidence of past HSV-2 infection | Clinical evaluation |
What does "HSV-1 index value 40" or "HSV-2 index value 40" mean? Very high index values (above 23–40) are reported differently on different platforms — some LabCorp reports display the maximum value as ">23.00" when the actual signal exceeds the assay's measurement ceiling. A result of ">23" or "40" on the same report means the antibody signal is beyond the measurable range — it is a very strong positive, not a specific titer value.
WHAT DOES "REACTIVE" OR "ABNORMAL" MEAN ON MY REPORT?
Lab reports for HSV-2 IgG use different terminology depending on the laboratory platform. These terms all mean the same thing — the test is positive:
| Term on your report | What it means |
|---|---|
| Reactive | Positive — antibodies detected above the threshold |
| Abnormal | Positive — result is outside the normal (negative) range |
| Reactive Abnormal | Positive — same as "reactive" |
| Positive | Positive — unambiguous |
| Out of Range | Positive — index value is above the reference range upper limit |
| H (with index number) | High — flagged as above the reference range; positive |
| Non-reactive | Negative — no antibodies detected above threshold |
| Negative | Negative |
| Equivocal | Borderline — neither clearly positive nor negative; see equivocal section |
Why do labs use "reactive" instead of "positive"? The term "reactive" is standard in serology reporting because antibody tests detect a reaction rather than directly detecting the organism. "Reactive" does not mean the infection is currently active — it means your blood reacted with the test antigen.
WHAT DOES AN EQUIVOCAL RESULT MEAN?
An equivocal HSV-2 IgG result (index value 0.90–1.09) means the test signal is in the borderline zone — too close to the cutoff to be classified as clearly positive or negative.
What to do with an equivocal result:
- Repeat the test in 12 weeks using the same laboratory platform (consistency is important for comparison)
- If the repeat result is still equivocal or turns positive, confirmatory testing with the inhibition assay or Western blot is appropriate
- An equivocal result alone should not be used to make a diagnosis of HSV-2 infection
- Equivocal results in the 0.90–1.09 range may represent very early seroconversion (if tested within the first weeks of exposure), a true borderline result that may resolve to negative, or a very weak true positive
Common specific equivocal values:
- 0.90: At the exact lower boundary of equivocal — earliest possible positive signal
- 0.91: Marginally equivocal — clinically equivalent to 0.90; repeat testing recommended
- 1.00–1.09: Equivocal zone — cannot classify without repeat testing
MOST COMMON HSV-2 IgG INDEX VALUES — EXACT LOOKUP
| Index value | Zone | Interpretation |
|---|---|---|
| <0.90 | Negative | No HSV-2 antibodies above threshold |
| 0.90 | Equivocal | At the exact lower boundary — repeat in 12 weeks |
| 0.91 | Equivocal | Marginally equivocal — clinically the same as 0.90 |
| 1.00–1.09 | Equivocal | Mid-equivocal zone — repeat testing needed |
| 1.10–1.50 | Low positive | Highest false positive zone — confirmatory testing essential |
| 1.20 | Low positive | Confirmatory testing strongly recommended before diagnosis |
| 2.50 | Low positive | Still in elevated false positive range — confirmatory testing recommended |
| 3.50 | Borderline transition | Lower false positive risk above this point; inhibition reflex still typical |
| 5.52–5.99 | Moderate positive | Inhibition reflex performed; most true positives |
| 6.00 | High positive | Well above threshold — true positive very likely |
| 14.00 | High positive | Markedly elevated; true positive |
| 23.00 / ">23.00" | Very high positive | Assay ceiling — result reported as ">23" when signal exceeds measurable range |
| 40+ (some platforms) | Very high positive | Same as ">23" — assay reporting maximum; not a specific titer |
Why exact values matter: Many users search their precise index value (e.g., "0.91 HSV-2 results," "HSV-2 index value 5.52," "HSV-2 index 23"). The table above provides direct interpretation for the most commonly searched values.
THE FALSE POSITIVE PROBLEM — THE MOST IMPORTANT CLINICAL NUANCE
The HSV-2 IgG ELISA has a known and clinically significant false positive rate, particularly in the low-positive range. This is one of the most important facts for anyone who has received a low-positive HSV-2 IgG result to understand.
What the evidence shows: False positives are well documented in the 1.10–3.5 index value range. Studies using Western blot as the confirmatory reference standard have found that a significant proportion of results in this range do not reflect true HSV-2 infection, particularly in populations with lower HSV-2 prevalence. This is why confirmatory testing is recommended before establishing a diagnosis based on a low-positive ELISA result alone. The false positive concern diminishes substantially at higher index values.
Why does this happen? The HerpeSelect IgG ELISA can produce low-level reactions in people who have antibodies to related antigens (cross-reactivity), in people with other viral infections, or due to non-specific assay variation. The lower the index value, the higher the likelihood that the result is a false positive.
The false positive risk by index value range:
| Index value range | False positive risk | What this means |
|---|---|---|
| 1.10–1.99 | Highest — confirmatory testing essential | A significant proportion of results in this range are false positives; do not diagnose without confirmation |
| 2.00–3.49 | Still elevated — confirmatory testing recommended | Lower false positive rate than 1.10–1.99 but still meaningful |
| 3.50–5.99 | Lower — inhibition reflex still often performed | Majority are true positives but inhibition assay adds confidence |
| ≥6.00 | Very low | Results at this level are almost always true positives |
What to do: The most important step for anyone with a low-positive HSV-2 IgG result (index 1.10–3.5) is confirmatory testing before accepting the diagnosis. The two main options are the HSV-2 IgG inhibition assay (automatically reflexed by LabCorp for index values 1.10–6.00) and the University of Washington HSV-2 Western blot (the gold standard confirmatory test, ordered separately).
HOW LIKELY IS IT THAT MY RESULT IS A TRUE POSITIVE?
| Index value | Likelihood of true positive | Recommended action |
|---|---|---|
| 1.10–1.50 | Lower — false positives are common in this range | Confirmatory testing essential before accepting diagnosis |
| 1.51–3.50 | Moderate — false positives still occur | Confirmatory testing strongly recommended |
| 3.51–6.00 | Higher — most are true positives, but confirmation adds confidence | Inhibition reflex typically performed; Western blot if any doubt |
| >6.00 | High — true positive very likely | Clinical evaluation; confirmatory testing usually not required |
This table reflects clinical guidance rather than a fixed mathematical probability — individual results depend on population prevalence, cross-reactivity factors, and assay variation. These categories align with how most infectious disease clinicians approach HSV-2 IgG interpretation.
THE HSV-2 IgG INHIBITION ASSAY — WHAT IT IS AND WHY IT MATTERS
When the initial HSV-2 IgG index value falls between 1.10 and 6.00 on the LabCorp platform, a second confirmatory test — the HSV-2 IgG Inhibition Assay (IA) — is automatically performed on the same sample. This is called a "reflex" test.
How the inhibition assay works: The sample is pre-treated with a competing HSV-2 antigen. If the antibodies in the sample are truly specific to HSV-2, they will be blocked (inhibited) by the competing antigen, causing the signal to drop. If the initial signal was not due to true HSV-2 antibodies (i.e., a false positive), the signal will not be significantly inhibited.
| Inhibition assay result | Meaning |
|---|---|
| Positive | The inhibition confirms HSV-2 antibodies are present — initial positive is supported |
| Negative / Not confirmed | Inhibition does not support the initial positive — likely false positive; consider Western blot |
| Equivocal | Inconclusive — Western blot may be needed |
If the inhibition assay is negative after a positive ELISA index: This is a strong indication that the initial positive was a false positive. Many clinicians will recommend the University of Washington Western blot for definitive clarification.
Why does this appear on my lab report? If your report shows "HSV-2 IgG Inhibition IA" as a second line item, it means the reflex test was automatically performed because your initial index value was between 1.10 and 6.00.
MOST COMMON HSV-2 IgG RESULTS
| Index value | Category | Typical interpretation |
|---|---|---|
| <0.90 | Negative | No HSV-2 antibodies detected |
| 0.90 | Equivocal (low) | At borderline — repeat in 12 weeks |
| 0.91 | Equivocal | Marginally equivocal — clinically same as 0.90 |
| 1.00–1.09 | Equivocal (mid-range) | Borderline — repeat testing needed |
| 1.10–1.99 | Low positive | Highest false positive zone — confirmatory testing essential |
| 2.00–3.49 | Low-moderate positive | Elevated false positive zone — confirmatory testing recommended |
| 3.50–5.99 | Moderate positive | Inhibition reflex typically performed; most are true positives |
| 6.00–23.99 | High positive | True positive very likely; clinical evaluation |
| >23 or ">23.00" | Very high positive | Assay ceiling exceeded — markedly elevated; true positive |
LOW POSITIVE VS HIGH POSITIVE — KEY DIFFERENCES
| Feature | Low positive (index 1.10–3.5) | High positive (index >6.0) |
|---|---|---|
| False positive risk | Meaningful — well documented in this range | Very low — results at this level are almost always true positives |
| Confirmatory testing | Strongly recommended before accepting diagnosis | Usually not required |
| Diagnostic confidence | Lower — cannot reliably confirm without additional testing | High |
| Inhibition reflex | Automatically performed (LabCorp, index 1.10–6.00) | Not performed (index exceeds reflex range) |
| Clinical approach | Confirm before counseling or treatment decisions | Proceed with clinical evaluation and management |
HSV-1 AND HSV-2 RESULTS TOGETHER — WHAT YOUR COMBINATION MEANS
Many patients receive both HSV-1 IgG and HSV-2 IgG results on the same panel. Interpreting them together adds important context:
| HSV-1 IgG | HSV-2 IgG | Most likely interpretation |
|---|---|---|
| Positive | Negative | Very common — most HSV-1 is oral (cold sore exposure); does not indicate genital herpes |
| Positive | Low positive (1.10–3.5) | The presence of HSV-1 antibodies slightly increases the chance the HSV-2 result is a false positive due to cross-reactivity; confirmatory testing is especially important |
| Positive | High positive (>6.0) | Exposure to both HSV-1 and HSV-2 is likely; each virus can be present independently |
| Negative | Positive (any level) | No HSV-1 immunity; HSV-2 exposure likely — confirmatory testing still appropriate for low positive values |
| Negative | Negative | No current IgG antibodies to either type detected |
| Equivocal | Equivocal | Both borderline — repeat testing in 12 weeks for both |
Important note on cross-reactivity: HSV-1 and HSV-2 share approximately 50% genetic sequence homology. High HSV-1 antibody levels can occasionally produce low-level cross-reactive signals on the HSV-2 assay. This is one reason why low-positive HSV-2 results in patients with strongly positive HSV-1 results should always be confirmed.
I TESTED POSITIVE FOR HSV-2 BUT HAVE NO SYMPTOMS — WHAT DOES THIS MEAN?
This is one of the most common and anxiety-provoking situations for people who receive an HSV-2 IgG positive result.
The most important fact: The majority of people with HSV-2 infection do not recognize symptoms. Studies consistently show that only approximately 10–25% of HSV-2-seropositive individuals are aware of their infection. Most people with HSV-2 have either never had a recognizable outbreak or have had symptoms that were too mild or atypical to be recognized as herpes.
What a positive HSV-2 IgG means in an asymptomatic person:
- Past exposure to HSV-2 has occurred — the immune system has mounted an antibody response
- The virus may be present in nerve ganglia and can reactivate
- Asymptomatic viral shedding occurs — the virus can be transmitted even without visible symptoms
- It does not mean you are currently having an active outbreak
What to do:
- If the result is low-positive (index 1.10–3.5): pursue confirmatory testing before accepting the diagnosis
- If confirmed positive: discuss with a clinician about transmission risk, suppressive antiviral therapy (which reduces shedding and transmission risk), and partner notification
- Antiviral medications (acyclovir, valacyclovir, famciclovir) are effective at reducing outbreak frequency and transmission risk
TRANSMISSION RISK TO PARTNERS — KEY FACTORS:
| Situation | Transmission risk |
|---|---|
| Confirmed positive, no symptoms, no antivirals | Present due to asymptomatic shedding — virus is transmitted without visible symptoms |
| Confirmed positive, daily suppressive antivirals | Meaningfully reduced — antivirals decrease asymptomatic shedding by approximately 50% |
| Confirmed positive, condoms + daily antivirals | Lowest — combination approach provides the greatest risk reduction |
| Active outbreak (symptomatic episode) | Highest — avoid sexual contact during outbreaks and for several days after |
| Low-positive result before confirmatory testing | Uncertain — confirmatory testing should occur before counseling on transmission risk |
TIMING AND THE WINDOW PERIOD
The HSV-2 IgG test has an important limitation related to timing:
| Time since exposure | IgG result interpretation |
|---|---|
| 0–4 weeks | Antibodies typically not yet detectable — a negative result does not exclude recent infection |
| 4–12 weeks | Antibodies developing — test may be false negative; repeat testing recommended |
| 12–16 weeks | Most infected individuals have detectable IgG antibodies by this point |
| >16 weeks | A negative result provides strong (but not absolute) evidence against past HSV-2 infection |
If you had a potential exposure within the past 12–16 weeks and the test is negative: The result should be repeated 12–16 weeks after the exposure before concluding negative status.
If you had a positive result within weeks of a known exposure: This could represent very early seroconversion (confirming recent infection) or a false positive — timing interpretation is important.
WHEN SHOULD I REPEAT THE HSV-2 IgG TEST?
| Situation | Repeat testing? | Timing |
|---|---|---|
| Exposure less than 12 weeks ago + negative result | Yes | Repeat at ≥12–16 weeks post-exposure |
| Equivocal result (0.90–1.09) | Yes | Repeat in 12 weeks using same laboratory platform |
| Low positive (1.10–3.5) without confirmatory testing | Yes | Request inhibition assay or Western blot before accepting diagnosis |
| Low positive + negative inhibition assay | Consider Western blot | University of Washington HSV-2 Western blot for definitive resolution |
| High positive (>6.0) with confirmatory test | Usually no | Result is reliably positive; retesting adds little diagnostic value |
| Monitoring known infection over time | Not routinely needed | Antibody levels fluctuate and do not reliably track disease activity |
Always use the same laboratory platform when repeating. Switching between assays (e.g., LabCorp HerpeSelect to Quest BioKit) can produce different index values that are not directly comparable, complicating interpretation.
WHAT TYPICALLY HAPPENS NEXT — CLINICIAN ACTION BY RESULT:
| Result | Typical next clinical step |
|---|---|
| Negative (<0.90) | No action needed; if recent exposure, schedule repeat at 12–16 weeks |
| Equivocal (0.90–1.09) | Repeat testing in 12 weeks using same platform |
| Low positive (1.10–3.5) | Confirmatory testing — inhibition assay or Western blot before diagnosis |
| Confirmed positive — all levels | Counseling on transmission risk; discuss suppressive antiviral therapy; partner notification |
| High positive (>6.0), no confirmation needed | Clinical evaluation; counseling; antiviral discussion |
| Positive + inhibition negative | Likely false positive — Western blot for definitive resolution; do not diagnose based on ELISA alone |
IgG VS IgM — THE KEY DISTINCTION
| Feature | IgG Antibody | IgM Antibody |
|---|---|---|
| What it indicates | Past or established infection — exposure occurred at some point | Theoretically indicates recent/acute infection |
| Reliability | High for HSV-2 IgG type-specific tests | Low — IgM herpes tests are unreliable; high false positive and cross-reactivity rates |
| Recommended for HSV-2 diagnosis | Yes — type-specific IgG is the standard | No — CDC and most guidelines do not recommend IgM testing for herpes diagnosis |
| Duration of positivity | Lifelong — IgG antibodies persist indefinitely | Short-lived (weeks to months) — but HSV IgM is often persistently positive due to test unreliability |
If your report shows "HSV-2 IgM positive": This result should be interpreted with caution. HSV IgM testing is known to be unreliable due to high rates of false positives and cross-reactivity with other herpes viruses (including the common CMV and EBV viruses). Most clinicians and guidelines rely on IgG type-specific testing, not IgM, for HSV-2 diagnosis.
HSV 2 IGG Screening Index
Every lab result you’ve ever had, charted and explained.
Healthmatters is a tracker for your lab results. Upload a report from any lab, any country — every marker charted and explained.
Start with my report →
Frequently Asked Questions
What does it mean when HSV-2 IgG is reactive?
What does an equivocal HSV-2 result mean?
What does a high HSV-2 index value mean — does a higher number mean worse disease?
Can the HSV-2 IgG test give a false positive?
Can an HSV-2 IgG positive result become negative over time?
What is the HSV-2 IgG inhibition assay?
I tested positive for HSV-2 but I've never had any symptoms. Is this possible?
Can the HSV-2 IgG test tell when I got infected?
¿Qué significa un resultado positivo de HSV-2 IgG? (What does a positive HSV-2 IgG result mean in Spanish?)
All our content is backed by peer-reviewed studies, academic research, and trusted medical sources. We’re committed to accuracy and transparency — see our editorial policy for details.
-
Polymerase chain reaction for detection of herpes simplex virus (HSV) DNA on mucosal surfaces: comparison with HSV isolation in cell culture
-
Incidence of Herpes Simplex Virus Type 2 Infections in Africa: A Systematic Review
-
Serological Screening for Genital Herpes: An Evidence Review for the U.S. Preventive Services Task Force [Internet]