How to Test for Herpes

Blood test for genital herpes

Genital herpes can be diagnosed by the use of a blood test (serologic testing). Blood tests can detect HSV antibodies even when you have no symptoms of herpes.

The accurate testing for type 2 herpes simplex virus detect IgG antibodies using a method called ELISA (enzyme-linked immunosorbent assay). The test produces a numerical result called ELISA index value.

Interpretation of test results: positive or negative?

Officially, index value greater than 1.1 is considered positive.

Index value below 0.9 indicates a negative result. If the IgG test is negative, and at least six months have passed from time of possible infection, you don’t have herpes.

Number between 0.9 and 1.1 is equivocal - antibody to HSV-2 may or may not be present.

Testing process

HerpeSelect test is the most commonly used HSV antibody test in the U.S. This test detects antibodies and can differentiate between oral herpes (HSV-1) and genital herpes (HSV-2).

No special preparation or appointment is required. Testing for genital herpes requires a simple blood sample.

You need to select a local testing facility near your home during the checkout process and you can start as early as today. Once you arrive at the lab, you’ll be in and out within 15 minutes.

How reliable is testing for herpes?

How accurate is the herpes blood test? Person infected with HSV produces virus-specific IgG antibodies that are detectable for life. Thus, detection of HSV IgG antibodies is a reliable indicator.

The sensitivity of the type specific IgG tests for HSV-2 is about 98% and for HSV-1 about 91% [1]. The specificity of the HSV-2 test is about 97%.

Most of the false positive results occur with index values between 1.1 and 3.5. Index values over 3.5 are definitively positive for HSV-2.

What does a positive herpes test indicate?

Positive antibody test does not indicate merely that one has been “exposed” to HSV. The presence of antibodies for HSV-2 indicates the genital herpes infection with the type 2 virus and means the person can potentially transmit it to a sexual partner at any time.

How long after contact can you test for herpes?

It takes time for immune system to develop antibodies after catching the first infection. This period is called the window period or seroconversion period. It takes about 3-6 weeks for a person to develop detectable antibodies for herpes virus. Virtually everyone will have detectable antibodies by 16 weeks after exposure.

A false-negative result from a blood test is possible if you have been infected recently.


  • 1. Philip SS, Ahrens K, Shayevich C, de la Roca R, Williams M, Wilson D, Bernstein K, Klausner JD. Evaluation of a new point-of-care serologic assay for herpes simplex virus type 2 infection. Clin Infect Dis. 2008 Nov 15;47(10):e79-82.

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