title: Generalisability of pharmacoepidemiological studies using restricted prescription data.
abstract: BACKGROUND
  Linking medication databases to disease registries enables population-based pharmacoepidemiology research. In Ireland, country-wide dispensing data is available only from the means-tested government-medical cards scheme. This restriction may impact generalisability of analyses based on these data.
  
  
  OBJECTIVE
  Gender was previously identified as predictor of card status so we aimed to compare women with and without medical cards at the time of ovarian cancer diagnosis.
  
  
  METHODS
  Ovarian cancers diagnosed 2001-2010 were identified from the National Cancer Registry Ireland. Age, region, deprivation, smoking, employment and marital status were evaluated using logistic regression for associations with card status. Cumulative incidence of de novo card receipt post-diagnosis was assessed.
  
  
  RESULTS
  1778 (52 %) of 3396 women with incident ovarian cancer had a card at diagnosis (<70:33 %; 70+:87 %). Within those <70, all variables were significantly associated with card status at diagnosis. 52 % of those without a card at diagnosis received one post-diagnosis.
  
  
  CONCLUSIONS
  Although medical card coverage within ovarian cancer patients is similar to the general population, various factors predict card status. Particularly within those under 70, external validity needs to be considered when interpreting pharamcoepidemiological analyses using these data.
authors.affiliation: National Cancer Registry Ireland, Building 6800, Cork Airport Business Park, Kinsale Rd, Cork City, Cork, Ireland. c.brown@ncri.ie.
authors.forename: C
authors.initials: C
authors.lastname: Brown
authors.affiliation: Trinity College Dublin, College Green, Dublin 2, Ireland.
authors.forename: T I
authors.initials: TI
authors.lastname: Barron
authors.affiliation: Trinity College Dublin, College Green, Dublin 2, Ireland.
authors.forename: K
authors.initials: K
authors.lastname: Bennett
authors.affiliation: National Cancer Registry Ireland, Building 6800, Cork Airport Business Park, Kinsale Rd, Cork City, Cork, Ireland.
authors.forename: D
authors.initials: D
authors.lastname: MacDonald
authors.affiliation: National Cancer Registry Ireland, Building 6800, Cork Airport Business Park, Kinsale Rd, Cork City, Cork, Ireland.
authors.forename: F
authors.initials: F
authors.lastname: Dwane
authors.affiliation: National Cancer Registry Ireland, Building 6800, Cork Airport Business Park, Kinsale Rd, Cork City, Cork, Ireland.|Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
authors.forename: L
authors.initials: L
authors.lastname: Sharp
mesh_terms: D000328:Adult; D000368:Aged; D016208:Databases, Factual; D011307:Drug Prescriptions / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007494:Ireland / Q000453:epidemiology; D016015:Logistic Models; D008499:Medical Records / Q000706:statistics & numerical data; D008875:Middle Aged; D010051:Ovarian Neoplasms / Q000453:epidemiology*; D017891:Pharmacoepidemiology / Q000706:statistics & numerical data*; D012042:Registries
keywords: External validity; Generalisability; Ovarian cancer; Pharmacoepidemiology; Prescriptions; Routine data