title: General practice performance in referral for suspected cancer: influence of number of cases and case-mix on publicly reported data.
abstract: BACKGROUND
  Publicly available data show variation in GPs' use of urgent suspected cancer (USC) referral pathways. We investigated whether this could be due to small numbers of cancer cases and random case-mix, rather than due to true variation in performance.
  
  
  METHODS
  We analysed individual GP practice USC referral detection rates (proportion of the practice's cancer cases that are detected via USC) and conversion rates (proportion of the practice's USC referrals that prove to be cancer) in routinely collected data from GP practices in all of England (over 4 years) and northeast Scotland (over 7 years). We explored the effect of pooling data. We then modelled the effects of adding random case-mix to practice variation.
  
  
  RESULTS
  Correlations between practice detection rate and conversion rate became less positive when data were aggregated over several years. Adding random case-mix to between-practice variation indicated that the median proportion of poorly performing practices correctly identified after 25 cancer cases were examined was 20% (IQR 17 to 24) and after 100 cases was 44% (IQR 40 to 47).
  
  
  CONCLUSIONS
  Much apparent variation in GPs' use of suspected cancer referral pathways can be attributed to random case-mix. The methods currently used to assess the quality of GP-suspected cancer referral performance, and to compare individual practices, are misleading. These should no longer be used, and more appropriate and robust methods should be developed.
authors.affiliation: Division of Applied Health Sciences, University of Aberdeen, Polwarth Building, Foresterhill, Aberdeen AB25 2ZD, UK.
authors.forename: P
authors.initials: P
authors.lastname: Murchie
authors.affiliation: Division of Applied Health Sciences, University of Aberdeen, Polwarth Building, Foresterhill, Aberdeen AB25 2ZD, UK.
authors.forename: A
authors.initials: A
authors.lastname: Chowdhury
authors.affiliation: Division of Applied Health Sciences, University of Aberdeen, Polwarth Building, Foresterhill, Aberdeen AB25 2ZD, UK.
authors.forename: S
authors.initials: S
authors.lastname: Smith
authors.affiliation: Division of Applied Health Sciences, University of Aberdeen, Polwarth Building, Foresterhill, Aberdeen AB25 2ZD, UK.
authors.forename: N C
authors.initials: NC
authors.lastname: Campbell
authors.affiliation: Division of Applied Health Sciences, University of Aberdeen, Polwarth Building, Foresterhill, Aberdeen AB25 2ZD, UK.
authors.forename: A J
authors.initials: AJ
authors.lastname: Lee
authors.affiliation: Detect Cancer Early Programme, The Scottish Government, St Andrews House, Regent Road, Edinburgh EH1 3DG, UK.
authors.forename: D
authors.initials: D
authors.lastname: Linden
authors.affiliation: Division of Applied Health Sciences, University of Aberdeen, Polwarth Building, Foresterhill, Aberdeen AB25 2ZD, UK.
authors.forename: C D
authors.initials: CD
authors.lastname: Burton
mesh_terms: D004739:England; D058006:General Practice; D006801:Humans; D009369:Neoplasms / Q000175:diagnosis / Q000453:epidemiology* / Q000473:pathology; D011320:Primary Health Care; D011785:Quality Assurance, Health Care; D012017:Referral and Consultation; D012606:Scotland