Background: Polymerase chain reaction (PCR) is becoming more common in diagnostic laboratories. In some instances, its value has been established. In other cases, assays exist, but their beneficial use has not been determined. This article summarizes findings from 3485 patients who underwent testing over a 6-year period in our laboratory.
Methods: A panel of PCR assays was used for the detection of a range of viruses associated with central nervous system (CNS) infections. PCR results were analyzed in conjunction with information about patient age and sex, the time between onset and specimen collection, and other variables. Medical chart review was conducted for 280 patients to gain diagnostic and epidemiologic insight with regard to cases of unresolved encephalitis.
Results: A total of 498 PCR-positive samples (14.3%) were detected. Enteroviruses accounted for the largest number (360 [72.3%]) of positive PCR results, followed by herpes simplex virus (76 [15.3%]), varicella-zoster virus (29 [5.82%]), and West Nile virus (WNV) (18 [3.61%]). Of 360 patients who tested positive for enterovirus, only 46 met the Centers for Disease Control and Prevention's encephalitis definition. It resulted in the greatest decrease (87.2%) in positive PCR results. Overall, the PCR positivity rate for specimens collected within 5 days after illness onset was 17.2%, compared with 8.6% for specimens collected > or =6 days after onset.
Conclusions: The value of PCR in the diagnosis of viral infections has been established. PCR is of lower value in the detection of WNV in CNS, compared with serological testing, but is of greater value in the detection of other arboviruses, particularly viruses in the California serogroup. Medical chart reviews indicated that apparent CNS infection resolves in approximately 50% of cases.