Herpes and STD Testing
There are two main types of blood tests used to detect herpes simplex virus (HSV): type-specific antibody tests and PCR (viral DNA) tests.
For routine blood testing to determine past or recent HSV infection, the following are used:
HSV type-specific IgG antibody test (recommended)
Detects IgG antibodies that indicate prior exposure to HSV.
Differentiates HSV-1 and HSV-2 (important because HSV-1 commonly causes oral cold sores and HSV-2 more often causes genital infection, though overlap occurs).
Best used at least 12–16 weeks after a suspected exposure for reliable results; testing too early can yield false negatives because antibodies may not have developed yet.
A positive result indicates infection at some point in the past; a negative result generally means no prior infection (if tested after the window period).
HSV IgM antibody test (generally not recommended for routine type determination)
Detects IgM antibodies that can appear early after infection.
IgM is less specific and less reliable for distinguishing HSV-1 vs HSV-2; false positives and cross-reactivity may occur.
Not recommended to determine type or to confirm recent infection because IgM can persist or reappear with reactivation.
HSV PCR (nucleic acid amplification test) on lesions or bodily fluids (for active infection)
Detects viral DNA and is the preferred test when active sores or lesions are present.
Can identify HSV-1 vs HSV-2 from lesion swabs, cerebrospinal fluid, or other specimens.
More sensitive than viral culture and useful for acute diagnosis (e.g., new genital or oral lesions, suspected herpes meningitis).
When to use which test:
If you have active sores: collect a swab of the lesion for HSV PCR (or culture if PCR unavailable). This gives the most definitive diagnosis and type identification.
If you have no lesions but want to know past exposure or your HSV-2 status: use a type-specific IgG antibody test (glycoprotein G-based assays are preferred).
If recent exposure (within a few weeks): consider waiting 12 weeks for IgG testing, or consult a clinician about repeat testing; PCR from symptoms is preferred if lesions develop.
Important considerations:
Not all antibody tests are equally accurate. Use FDA-cleared, type-specific tests (glycoprotein G-based). Ask your provider or lab which assay they use.
False positives are possible, particularly for low-titer results. If results are unexpected, repeat testing or confirmatory testing may be advised.
Interpret results with clinical context and counseling: a positive HSV IgG means prior exposure, not necessarily symptomatic disease; negative testing does not rule out very recent exposure.
If testing for pregnancy, neonatal risk, or suspected central nervous system disease, discuss the optimal tests with your clinician (PCR on cerebrospinal fluid may be indicated for suspected HSV encephalitis).
Either way get tested, ask partner to be tested.
Tested, tested, and get tested!
