title: A comparison of variability in Papanicolaou and liquid-based cytology inadequacy rates using Shewhart control charts.
abstract: OBJECTIVE
  To use Shewhart control charts to compare variability in inadequacy rates from Papanicolaou (Pap) and liquid-based cytology (LBC).
  
  
  METHODS
  Retrospective analysis of quality assurance data.
  
  
  METHODS
  Eleven Welsh cytology laboratories.
  
  
  METHODS
  Shewhart 'p' charts were plotted for proportions of slides reported as inadequate. Charts were compared for statistical control.
  
  
  METHODS
  Evidence of statistical control in the processes.
  
  
  RESULTS
  Control charts allowed easy interpretation of patterns in the data. Variability in inadequacy rates was much lower for LBC than for Pap cytology.
  
  
  CONCLUSIONS
  Monitoring inadequate rates with Shewhart charts provides more information than tabular monitoring reports, assisting in quality improvement. With respect to inadequacy rates, LBC is less variable than Pap cytology.
authors.affiliation: National Public Health Service for Wales, Temple of Peace and Health, Cardiff, UK. rosemary.fox@nphs.wales.nhs.uk
authors.forename: R
authors.initials: R
authors.lastname: Fox
authors.forename: A B J
authors.initials: AB
authors.lastname: Nix
authors.forename: H
authors.initials: H
authors.lastname: Fielder
mesh_terms: D005260:Female; D006801:Humans; D008403:Mass Screening; D008499:Medical Records; D015588:Observer Variation; D065006:Papanicolaou Test; D012189:Retrospective Studies; D002577:Uterine Cervical Diseases / Q000175:diagnosis*; D014626:Vaginal Smears / Q000379:methods / Q000706:statistics & numerical data; D014852:Wales