Chicken Pox Signs
Chicken Pox is often diagnosed clinically on the basis of a generalized maculopapulovesicular rash. The clinical diagnosis of varicella in the United States has become increasingly challenging as a growing proportion of cases occur in vaccinated people in whom disease is mild and rash is atypical. Although not routinely recommended, laboratory diagnosis is likely to become increasingly useful. For laboratory confirmation, skin lesions are the preferred specimen. Vesicular swabs or scrapings and scabs from crusted lesions can be used to identify varicella-zoster virus by PCR or direct fluorescent antibody. In the absence of vesicles or scabs, scrapings of maculopapular lesions can be collected for testing.
Serologic tests may also be used to confirm disease: A significant rise in serum varicella IgG from acute- and convalescent-phase samples by any standard serologic assay can confirm a diagnosis retrospectively; these antibody tests may not be reliable in immunocompromised people. Testing for varicella-zoster IgM by using commercial kits is not recommended, because available methods lack sensitivity and specificity; false-positive IgM results are common in the presence of high IgG levels.