In 1994, an international group of interested clinicians and biostatisticians met to discuss the design of clinical trials in
herpes zoster. They agreed that trials in
herpes zoster should have prospectively agreed definitions of all outcome measures and plans for data analysis. In immunocompetent individuals, in whom
pain is the major outcome measure, trials should only include patients over the age of 50 years, and for those recruited within 72 h of
rash onset, should be designed to demonstrate superiority of any new
therapy over existing
antivirals. The primary endpoint should be time to cessation of
pain for at least 4 weeks and, for the purposes of statistical analysis of its duration, the
pain associated with
herpes zoster ought to be considered as a continuum. All other variables, including the incidence of post-herpetic
neuralgia and effects upon quality of life should be considered as secondary end-points. Evaluation of treatment effects on primary endpoints should be based upon an intent-to-treat (ITT) analysis and subgroup analysis should be used only to support the findings of the ITT analysis. These elements of good study design should be borne in mind in the evaluation of current and future trails of
antiviral drugs in
herpes zoster.