Investigations
1st investigations to order
clinical diagnosis
Test
Usually does not require tests or culture.
Result
typically presents with dermatomal pain followed by a rash in the affected area
Investigations to consider
polymerase chain reaction (PCR)
Test
Detects DNA in fluids and tissues. The most sensitive and specific method.[75]
Samples from lesions are useful in differentiating from herpes simplex.
Blood PCR can be used as a diagnostic test when there is no rash (zoster sine herpete).
Disseminated zoster in the immunocompromised is diagnosed by PCR on blood and lesions.
Result
positive for varicella DNA
immunohistochemistry
Test
Using a modified Tzanck technique, cells are scraped from the base of a lesion with a scalpel blade or the bevel of a large-blade needle, smeared on a glass slide, and stained with fluorescein-conjugated monoclonal antibodies to detect viral glycoprotein. This method is more sensitive than viral culture.[76][77]
Result
positive stain for varicella virus
vesicular fluid culture
Test
Recovery of the virus is dependent on the stage of the lesions and quality of the specimen. This method has lower sensitivity than immunofluorescence as a result of virus lability.[1]
Result
positive varicella virus in culture
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