Laboratory Evaluation of Suspected Encephalitis

Laboratory Evaluation of Suspected Encephalitis
CSF PCR

STRATEGY

  • urgent diagnosis needed to validate proper therapy
  • isolation of HSV from culture is the reference method for diagnosis
  • DNA PCR on CSF obtained by lumbar puncture is becoming the gold standard
  • DFA performed on brain touch prep in the current case (LP contraindicated due to possible herniation risk
  • comprehensive virus isolation from brain within days confirmed HSV-1

METHODS

  • lyse virions and extract DNA
  • PCR with two sets of primers
  • pol gene of HSV, 179 bp amlpicon
  • glycoprotein B gene of HSV, 148 bp amplicon
  • does not amplify CMV, VZV, HHV 6
  • cut pol amplicons with HhaI
  • cleaves HSV-1 amplicon at a single site, two fragments
  • cleaves HSV-2 amplicon at two sites, three fragments
  • separate products on agarose gel with EtBr

NIAID Collaborative Antiviral Study Group. J Infect Dis 171:857, 1995
Tang Y-W et al. J Clin Microbiol 37:2127, 1999

 
Biopsy +
Biopsy -
PCR +
53
3
PCR -
1
44
  • sensitivity 98%
  • specificity 94%
  • positive predictive value 95%
  • negative predictive value 98%

NIAID Collaborative Antiviral Study Group. J Infect Dis 171:857, 1995