What is the role of lab studies in the diagnosis of postherpetic neuralgia (PHN)?

Updated: Mar 06, 2018
  • Author: W Alvin McElveen, MD; Chief Editor: Robert A Egan, MD  more...
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  • No laboratory work is usually necessary in cases of postherpetic neuralgia (PHN).

  • Results of cerebrospinal fluid (CSF) evaluation are abnormal in 61%.

    • Pleocytosis is observed in 46%, elevated protein in 26%, and varicella zoster virus (VZV) DNA in 22%.

    • These findings are not predictive of the PHN clinical course.

  • Viral culture or immunofluorescent staining may be used to differentiate herpes simplex from herpes zoster in cases that are difficult to distinguish clinically.

  • Antibodies to herpes zoster can be measured. A 4-fold increase has been used to support the diagnosis of subclinical herpes zoster (zoster sine herpete). However, a rising titer secondary to viral exposure rather than reactivation cannot be ruled out.

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