Investigation - Arma

Antigen detection: Direct fluorescent antigen assay is more sensitive than viral culture. Using a modified Tzanck technique, cells are scraped from the base of the lesion with a scalpel blade or the bevel edge of a large-gauge needle, smeared on a glass slide, then stained using fluorescein-conjugated monoclonal antibodies to detect viral glycoproteins. Unlike a traditional Tzanck smear, direct fluorescent antigen assay (DFA) can distinguish between herpes simplex virus and VZV.


Serology: Patients with herpes zoster will, by definition, be VZV seropositive at the onset of illness. Although some patients will show an enhanced VZV antibody titer after an episode of herpes zoster, serology is not a very sensitive or specific diagnostic method. Most laboratories use enzyme-linked immunosorbent assay (ELISA) or latex agglutination methods; more sensitive assays such as the fluorescent antibody to membrane antigen test and glycoprotein ELISA are not widely available. The latex agglutination test is generally more sensitive than ELISA for detecting VZV antibody
after natural infection or vaccination. Commercial ELISA tests range in sensitivity from 86%-97% and range in specificity from 82%-99% in detecting antibody after natural varicella infection but are less reliable for detecting antibody after vaccination.

PCR: Polymerase chain reaction (PCR) techniques use a piece of the DNA of the virus, which is then replicated millions of times until the virus is detectable. This technique is expensive but is useful for detecting VZV DNA in fluids (e.g., cerebral spinal fluid). Not widely available. Sensitivity and specificity are unknown. Polymerase chain reaction on cerebral spinal fluid is the test of choice along with antibody testing for VZV in patients with suspected VZV myelitis, vasculopathy or zoster sine herpete (herpes zoster with abnormal skin sensations and pain in a dermatomal distribution but without a rash).

http://www.acpinternist.org/archives/2007/03/herpes.pdf