Detection of herpes simplex virus DNA in dried blood spots making a retrospective diagnosis possible.

BACKGROUND: Herpes simplex virus (HSV) infections in neonates are associated with life-threatening disease. Early diagnosis and treatment with antiviral therapy has decreased the morbidity, mortality and long-term sequelae in surviving children. The aim of the study was to investigate if herpes simplex virus DNA detection in dried blood spots on filter papers (Guthrie cards) sampled for screening of metabolic diseases may contribute to early diagnosis of neonatal HSV infection and enable pre-emptive therapy.
METHODS: For detection of HSV-1 and -2 DNA, two different DNA extraction methods were evaluated. A minimal essential medium (MEM) extraction method was found superior and was used in combination with detection of HSV-1 and -2 DNA by PCR in dried blood spots from children with verified neonatal HSV infection. Cards from 28 children were included. The onset of illness varied from day 0 to 42 days and was the result of different types of maternal infection (27 cases) and an external source (one case).
RESULTS: HSV DNA was detected in seven of the 28 Guthrie cards, two were HSV-1 and five were HSV-2 DNA positive. Positive dried blood spot cards were sampled within the interval 5 days before, to 6 days after onset of neonatal herpes. In cases of late onset CNS disease, viremia, was not demonstrable at the age of 3-5 days, the time period when the blood spot cards are normally sampled.
CONCLUSION: Viremia, the prerequisite for demonstrating HSV DNA in dried blood spot cards preceded the onset of illness by up to 5 days and lasted at least up to 6 days thereafter. Analysis of HSV DNA in dried blood spot cards may be of value in the diagnostic arsenal for early onset of neonatal herpes and also have a role in the follow up of a child exposed at delivery. As the majority of the later onset neonatal herpes encephalitis cases are missed, a large-scale neonatal screening does not seem appropriate.