MedifocusHealth

Physical Examination

Examination of the affected skin usually reveals the characteristic rash. Involvement of the face (especially the nose - called Hutchinson's sign) may necessitate examination of the eyes by an ophthalmologist. Depending on the site of the rash, a neurologic examination may also be performed.

Laboratory Evaluation

Laboratory diagnosis of varicella-zoster virus infections is well established and generally available in the United States. The virus can be isolated from the vesicular skin lesions of varicella and zoster, especially in the first 1 to 2 days after onset of rash.

The following laboratory tests may be used to detect the virus from the vesicular skin lesions:

• Tzanck smear - requires scraping the base of an early lesion
• Culture - the "gold standard" - very specific but not very sensitive, results take 1-2 weeks to obtain. It is not useful for very long beyond the vesicular stage of the rash
• Direct immunofluorescence - provides rapid and accurate detection of varicella-zoster virus from lesion scrapings
• Molecular techniques - especially useful in distinguishing the wild-type and vaccine strains of the virus; this has been helpful in evaluating patients who have been vaccinated and develop a vesicular rash
• Polymerase chain reaction (PCR) - the most sensitive and specific test, but also very expensive; results take about one day to obtain
• Electron microscopy - can be extremely useful in rapidly distinguishing between herpesvirus and poxvirus infections.