In most instances, herpes simplex recidivans can be diagnosed clinically from the historical data and a typical skin lesion. There are occasions however, where special circumstances make laboratory confirmation desirable.
A smear of material from a fresh, ruptured blister base is placed on glass slide and immediately stained with Giemsa or some similar stain. A positive smear will show her-pesvirus effect by the presence of keratinocytes with balloon nuclei and multinucleated giant cells with similar changes (see Photos 13,14). This test is rapid, inexpensive, and can be performed with equipment that is readily accessible. Sensitivity in experienced hands using material from a fresh vesicle approaches or exceeds 70%. In pustular lesions, sensitivity diminishes. This test does not distinguish between HSV-1, HSV-2, or herpes zoster virus.
Biopsy of a herpetic lesion shows pathognomonic features, but is usually done only to investigate a lesion that is clinically atypical. Biopsy does not distinguish HSV-1 from HSV-2 or herpes zoster virus (HZV), and adds nothing if the lesions are clinically diagnostic.
These titers rise rapidly during primary infection and are valuable if acute and convalescent titers are obtained. In recurrent disease, titers show little change and are of no value. Western blot and enzyme-linked immunoassay tests, if available, are sensitive and will distinguish one virus from the other.
Culture from fresh blister material can be very sensitive (80% +) and will distinguish HSV-1 from HSV-2 and HZV. Culture is indicated to confirm the diagnosis in unusual cases, to distinguish HSV-1 infection from HSV-2, and for medical-legal reasons in cases of rape and child molestation. In otherwise clinically typical cases, culture is unnecessary and the diagnosis can usually be confirmed by Tzanck smear or RIF test. Cultures are expensive and slow, and must be obtained from fresh lesions or their sensitivity falls precipitously.
This test employs a monoclonal antibody system and exhibits a sensitivity of about 65%. In addition to speed, this test can distinguish among HSV-1, HSV-2, and HZV. The specimen consists of a smear from a blister. The test is practical and reproducible. Results are available within 1 hour or less after receiving the specimen.
Polymerase Chain Reaction (PCR)
PCR testing performed from blister specimens shows a sensitivity of 83%, which is equivalent to culture. This test is rapid and can distinguish HSV-1 from HSV-2 and HZV. In addition, the test is positive when performed from crusts and with material from involuting lesions where culture, Tzanck, and RIF results are less reliable. The technology is expensive and not universally available at present. PCR should be reserved for atypical cases or unusual circumstances. HSV and HZV can be distinguished within 6 hours, and HSV types by 24 hours.
Because sexually transmitted diseases are occasionally transmitted concurrently, a serologic test for syphilis should be done when herpes genitalis is diagnosed. Authorization should also be requested to run serologies for HIV.
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