Which laboratory test is essential for confirming a diagnosis of genital herpes?

Viral culture is the gold standard test for confirming a diagnosis of genital herpes, particularly when a patient presents with active lesions. This test involves taking a sample from the sore or blister and attempting to grow the herpes simplex virus (HSV) in a laboratory setting. If the virus is present, it will proliferate in the culture, thus confirming the diagnosis.

While serologic testing is useful for detecting antibodies to HSV and can help diagnose herpes infections retrospectively, it does not confirm an active infection. Serological tests can identify whether someone has been exposed to the virus in the past but do not provide real-time confirmation of an active, symptomatic outbreak.

White blood cell count is not specific to herpes and is used to assess immune response generally, while a glucose tolerance test is unrelated to herpes and is used to evaluate diabetes. Therefore, in the context of confirming genital herpes specifically during active outbreaks, viral culture is the preferred and essential test.