Use of Blood Polymerase Chain Reaction Testing for Diagnosis of Herpes Simplex Virus Infection
Cantey JB, Mejías A, Wallihan R, et al
J Pediatr. 2012;161:357-361
Study Summary
Polymerase chain reaction (PCR) is now the test of choice for identifying central nervous system infection caused by herpes simplex virus (HSV). This study represents a longitudinal review of HSV PCR testing at 2 pediatric academic medical centers in the United States to determine the clinical features of children positive for serum HSV through PCR testing. This was a retrospective review of all patients who had a serum HSV PCR test at the participating institutions from 2005 to 2010. Cantey and colleagues focused on children with 1 positive blood HSV PCR test and reviewed their charts for demographic, clinical, and other data. They defined a neonatal HSV infection as occurring before 42 days of age.
During the study period, more than 700 patients received blood HSV PCR testing. Of those children, 294 were infants younger than 42 days old. A positive HSV PCR test was found in 45 total patients (6.1%), 21 of whom were infants. Of these infants, approximately 1 in 4 were diagnosed with skin, eye, and mouth HSV disease; another 25% were diagnosed with central nervous system HSV disease; and approximately 50% had disseminated HSV disease. One third of the neonatal HSV patients in this study died. For 2 of those infants, the blood HSV PCR was the only positive HSV test. In another 4 children, the blood HSV PCR was the first test that was positive.
Among the 24 older children with positive blood HSV PCR tests, 50% were immunocompromised. Another 29% suffered from atopic dermatitis. Mucocutaneous lesions were much more common, occurring in 92% of these older children, and 13% of the older children died. In 4 of the older children, the blood HSV PCR was the only positive test, and it was the first positive test in another 7 of these children, all of whom had vesicular lesions that would have clinically suggested an HSV diagnosis. Cantey and colleagues concluded that HSV PCR testing on serum samples can be a useful adjunct in the diagnosis of HSV, especially among young infants who are much less likely than older children to have mucocutaneous lesions.
Viewpoint
It is worth noting that in slightly more than 10% of the cases in this series, the blood PCR test was the only positive HSV test. That finding alone is of interest, but the investigators' additional observation about the relative infrequency of mucocutaneous lesions in infants and the finding that 50% of the tested infants had disseminated disease shows that infants, particularly neonates, are a logical group in whom to perform blood HSV testing. It is difficult to know whether the percentages reported in these data would be the same among all infants who are tested for HSV because this study looked only at the children who had serum HSV PCR testing. For example, there may have been particular details about untested children that dissuaded the treating providers from sending HSV blood samples. It would be interesting to see a similar breakdown of a series of infants who were tested for HSV through both methods to be able to compare sensitivity and specificity of the different tests.
Abstract