title: Application of a propensity score to adjust for channelling bias with NSAIDs.
abstract: OBJECTIVE
  To compare the relative risks of upper GI haemorrhage (UGIH) in users of Newer versus Older, non-specific NSAIDs when adjusted for channelling bias by regression on individual covariates, a propensity score and both.
  
  
  METHODS
  Cohort study of patients prescribed NSAIDs between June 1987 and January 2000. Exposure to Newer and Older non-specific NSAIDs was identified, and risk factors evaluated for each patient. Results of multiple covariate analyses and the propensity scoring technique to assess potential channelling bias in comparisons between Newer and Older non-specific NSAIDs were compared.
  
  
  RESULTS
  This study included 7.1 thousand patient years (tpy) exposure to meloxicam, 1.6 tpy exposure to coxibs, and 628 tpy exposure to Older non-specific NSAIDs. Patients receiving Newer NSAIDs were older, more likely to have a history of GI symptoms, and at higher risk for GI complications. Adjusting for these risk factors reduced the relative risks of UGIH on meloxicam and coxibs versus Older non-specific NSAIDs to 0.84 (95%CI 0.60, 1.17) and 0.36 (0.14, 0.97) respectively.
  
  
  CONCLUSIONS
  Channelling towards high GI risk patients occurred in the prescribing of Newer NSAIDs. Propensity scores highlighted the markedly different risk profiles of users of Newer and Older non-specific NSAID. Correcting for channelling bias, coxib exposure, but not meloxicam exposure, was associated with less UGIH than Older non-specific NSAID exposure. In the present study, corrections made by regression on a propensity score and on individual covariates were similar.
authors.affiliation: Medicines Monitoring Unit, Department of Medicine & Therapeutics, University of Dundee, Ninewells Hospital & Medical School, Dundee, UK. steve.morant@btinternet.com
authors.forename: S V
authors.initials: SV
authors.lastname: Morant
authors.forename: D
authors.initials: D
authors.lastname: Pettitt
authors.forename: T M
authors.initials: TM
authors.lastname: MacDonald
authors.forename: T A
authors.initials: TA
authors.lastname: Burke
authors.forename: J L
authors.initials: JL
authors.lastname: Goldstein
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000009:adverse effects* / Q000627:therapeutic use; D015331:Cohort Studies; D016861:Cyclooxygenase Inhibitors / Q000009:adverse effects* / Q000627:therapeutic use; D016208:Databases, Factual; D017723:Drug Utilization Review; D005194:Family Practice / Q000706:statistics & numerical data*; D005260:Female; D006471:Gastrointestinal Hemorrhage / Q000139:chemically induced* / Q000453:epidemiology; D006801:Humans; D008297:Male; D000077239:Meloxicam; D008875:Middle Aged; D010003:Osteoarthritis / Q000188:drug therapy*; D017891:Pharmacoepidemiology; D012044:Regression Analysis; D012307:Risk Factors; D012737:Sex Factors; D013843:Thiazines / Q000009:adverse effects* / Q000627:therapeutic use; D013844:Thiazoles / Q000009:adverse effects* / Q000627:therapeutic use; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D016861:Cyclooxygenase Inhibitors; D013843:Thiazines; D013844:Thiazoles; D000077239:Meloxicam