Diagnosis:

Clinical diagnosis of genital herpes is limited in accuracy. First, Herpes Simplex virus (HSV) is only one of several diseases characterized by genital ulcers. More importantly, many persons are unaware that their symptoms are those of herpes. The lumbosacral sensory ganglia, where HSV is most likely to persist, innervate the lower half of the body as well as the genitalia. The typical lesions may not appear, and recurrences may be at different locations along a dermatome. Women may experience only prodromal symptoms, such as burning or tingling; have single ulcers, fissures, or erosion; or experience erythema or edema as the primary symptom. One author has argued that HSV-2 should be considered the cause of any such symptoms below the waist until that diagnosis is excluded.

Available tests for herpes include both culture and PCR-DNA testing for viral shedding, and the use of blood tests to screen for previous exposure. Which test to use and how to interpret the results is a key decision for clinicians. Confirmation of current infection requires direct detection of the virus with culture or PCR testing at the time of clinical diagnosis. Type-specific serology testing in the absence of symptoms establishes previous exposure and antibody response.

Cultures are most accurate early in the sequence of clinical outbreaks. Fluid collected from intact blisters will grow out in culture more than 90% of the time. By the time the lesions have crusted over, only about 25% of cultures will be positive. When PCR testing is available, its use should be considered in preference to cultures, because it is more sensitive. Wald et al. reported a four-fold increase in positive tests in a direct comparison of culture to PCR assay. PCR testing will also confirm viral shedding whether or not lesions are present. The 2006 CDC Sexually Transmitted Diseases Treatment Guidelines note that PCR testing is more sensitive, but has not yet been approved by the US Food and Drug Administration for the testing of genital specimens.

When using serology to confirm a clinical HSV diagnosis, the most common glycoprotein-G type specific tests are highly accurate. Various HSV-2 antibody tests have reported sensitivity between 90% and 100% and specificity between 91% and 100%.Women who are offered serology testing must understand the limitations of the tests. Serology cannot date the onset of infection or identify the locus of shedding. However, information regarding whether one is infected with HSV-1 or HSV-2 can prove useful in discussing risks for recurrence. In general, genital HSV-1 causes a severe initial outbreak but fewer recurrences than HSV-2. For the purposes of treatment, type-specific testing is useful but not essential, because treatment regimens do not vary by virus type.