title: Prevalence of Churg-Strauss syndrome, vasculitis, eosinophilia and associated conditions: retrospective analysis of 58 prescription-event monitoring cohort studies.
abstract: OBJECTIVE
  Churg-Strauss syndrome is characterised by hypereosinophilia, systemic vasculitis and asthma. The cause is usually unknown, but there have been reports of an association with particular drugs, including anti-asthma drugs. Our aim was to estimate the prevalence of Churg-Strauss syndrome and related conditions in post-marketing safety studies of new anti-asthma drugs.
  
  
  METHODS
  We accessed the prescription-event monitoring (PEM) database of the Drug Safety Research Unit (DSRU). This database currently has information on 622 294 patients observed during 58 completed PEM studies of individual drugs, including 35 799 patients in studies of new anti-asthma drugs.
  
  
  RESULTS
  Overall, four cases of Churg-Strauss syndrome were identified during these studies, giving a period prevalence rate of 6.8 (95% confidence limits [CL]: 1.8-17.3) per million patient-years of observation. The period prevalence of Churg-Strauss syndrome was significantly greater in the PEM cohorts of anti-asthma drugs (64.4 million patient-years of observation; 95% CL: 13.3-188.1), than the other PEM drug cohorts (1.8 per million patient-years of observation; 95% CL: 0.05-10.2) (rate ratio: 35.1; 95% CL: 2.8-1839.9; p=0.002).
  
  
  CONCLUSIONS
  Our data provide estimates of the prevalence of Churg-Strauss syndrome and related conditions in cohorts of asthmatic patients, which may be useful during the pharmacovigilance of new asthma drugs, including the new leukotriene receptor antagonists.
authors.affiliation: Drug Safety Research Unit, Bursledon Hall, Blundell Lane, Southampton SO31 1AA, UK.
authors.forename: R M
authors.initials: RM
authors.lastname: Martin
authors.forename: L V
authors.initials: LV
authors.lastname: Wilton
authors.forename: R D
authors.initials: RD
authors.lastname: Mann