Molecular Blood Test Diagnoses Herpes Simplex Virus Infection

Polymerase chain reaction (PCR) is now the test of choice for identifying central nervous system infection caused by herpes simplex virus (HSV).

A longitudinal review of HSV PCR testing at two pediatric academic medical centers in the USA determined the clinical features of children positive for serum HSV through PCR testing.

Scientists at the University of Texas Southwestern Medical Center (Dallas, TX, USA) in collaboration with others carried out a retrospective review of all patients who had a serum HSV PCR test at the participating institutions from 2005 to 2010. The study focused on children with one 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.

More than 700 patients received blood HSV PCR testing during the study period. Of those children, 294 were infants younger than 42 days old. A positive HSV PCR test was found in 45 patients (6.1%), 21 of whom were infants. Of these infants, approximately 25% 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 two of those infants, the blood HSV PCR was the only positive HSV test. In another four 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 four of the older children, the blood HSV PCR was the only positive test, and it was the first positive test in another seven of these children, all of whom had vesicular lesions that would have clinically suggested an HSV diagnosis. The authors 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. The study was published in the August 2012 edition of the Journal of Pediatrics.

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University of Texas Southwestern Medical Center