Receiving an “abnormal” or positive result on a herpes test can be confusing. Herpes Simplex Virus (HSV) testing is typically performed either to investigate current symptoms, such as sores or blisters, or to screen for past exposure. Understanding what the test measures is the first step in clarifying what a positive result indicates. The meaning of an abnormal result depends highly on the specific type of test conducted.
Types of Herpes Tests and What They Measure
Herpes testing falls into two main categories, each designed to detect a different aspect of the infection. The first category involves viral detection tests, such as Polymerase Chain Reaction (PCR) or viral culture, performed using a swab from an active lesion or sore. A positive result means the Herpes Simplex Virus is currently active and shedding at the site that was swabbed. This test is highly accurate for confirming an active outbreak but cannot determine past exposure if no lesions are present.
The second category is the antibody test, a blood test used for screening or diagnosing past exposure when a person has no active symptoms. This test looks for Immunoglobulin G (IgG) antibodies, which the body’s immune system produces in response to the virus. A positive antibody test result means the body has been exposed to HSV at some point, causing the immune system to produce these long-lasting antibodies. Since it can take weeks to months for the body to produce enough antibodies, a very recent infection may produce a false-negative result.
Interpreting Positive and Equivocal Results
A positive result on an antibody test is usually followed by a breakdown of the specific virus type found, Herpes Simplex Virus Type 1 (HSV-1) or Type 2 (HSV-2). The test uses type-specific serologic assays to detect IgG antibodies, differentiating which viral type the body has encountered. While HSV-1 is traditionally associated with oral herpes (cold sores) and HSV-2 with genital herpes, both types can cause infection in either location, though HSV-2 is more commonly linked to genital infection.
The reliability of a positive antibody test is closely tied to a numerical measure called the index value, which represents the concentration of antibodies detected in the blood. A high positive index value, typically above 3.5 or 5.0, strongly indicates a true positive result, confirming past exposure to the virus. However, index values in the low-positive range, often between 1.1 and 3.5, carry a significant risk of being a false positive, particularly for HSV-2.
The poor specificity of many commercial tests at low index values means the antibodies may be cross-reacting with other viruses, leading to a false diagnosis. For HSV-2, studies show that a low index value (1.1–3.0) may be falsely positive up to half the time. Another possible result is “equivocal,” meaning the antibody level falls into a gray area where the test cannot definitively confirm a result. An equivocal result often requires repeat testing in four to six weeks to allow the body to produce a clearer antibody response.
Next Steps Following an Abnormal Result
If an initial antibody test returns a low-positive or equivocal result, the most important next step is to seek confirmatory testing. The Western blot assay, often considered the gold standard for accuracy, is recommended to rule out a false positive result. This is especially true for low-positive HSV-2 results, where the accuracy of the initial test is often questionable.
Once a diagnosis is confirmed, consulting with a healthcare provider is necessary to discuss the result in the context of your health and history. Your provider can help determine the likelihood of future outbreaks and the risk of transmission to partners. Management strategies may include antiviral medications, which can be taken episodically at the first sign of an outbreak or as suppressive therapy to reduce the frequency of recurrences and lower the risk of transmission. Understanding the diagnosis also enables informed conversations with sexual partners about the status and necessary precautions.