NEW YORK (Reuters Health) – A new 2-hour test for herpes simplex virus (HSV) identifies women in labor who have the virus in their genital secretions, when thereís still time to prevent transmission of this devastating infection to their newborns.

Without prophylaxis, HSV infection in newborns causes disseminated or central nervous system disease in about half of cases, investigators note in the June issue of Obstetrics & Gynecology. Up to 30% of victims die, and up to 40% of survivors will have neurologic damage. The presence of HSV in the maternal genital tract can raise the risk of neonatal HSV by more than 300.

When herpes lesions are present, the only strategy for preventing neonatal herpes is cesarean delivery — but most women with HSV do not have lesions. Results of viral cultures taken during labor are not available soon enough for effective interventions to be taken, and false positives are common.

The new test, developed by Dr. Carolyn Gardella and colleagues at the University of Washington, Seattle, is an automated, self-contained polymerase chain reaction (PCR) assay that can be used by ìany trained laboratory technician,î with results reported back to the delivery room within 2 hours.

The researchers tested samples from 732 individuals, including 299 negative controls, 211 swabs from nonpregnant patients with genital herpes lesions, and 206 mucocutaneous genital swab samples from pregnant women in labor. Samples were tested by the Rapid PCR assay and compared with the ìgold standardî TaqMan HSV PCR assay.

Using a cutoff of 150 copies/mL in each of two wells, the Rapid PCR assay detected HSV DNA in 207 swabs, compared with 212 swabs by the TaqMan. More specifically, both tests were positive in four samples, both were negative in 195, only Rapid PCR was positive in one, and only TaqMan was positive in six.

Test sensitivity was 99.6%, specificity was 96.7%, positive predictive value was 96.7%, and negative predictive value was 99.6% in a population with HSV shedding prevalence of 10.8%.

The authors say their assay would ideally be used with serology results ìto define how best to manage neonates exposed to HSV at delivery.

For example, a woman with HSV-2 in her genital tract during labor but whose serology test is negative indicating a new infection — is at high risk for passing HSV onto her newborn, and c-section may be warranted, especially if the membranes are ruptured. On the other hand, a course of intrapartum acyclovir may be sufficient for women with HSV-2-positive genital secretions and antibodies to the virus.

On the other hand, infants of women with HSV-1 are at high risk regardless of whether the mother has a new infection or a reactivation.

Reference:

Obstet Gynecol 2010;115:1209-1216.