title: Performance of the disease risk score in a cohort study with policy-induced selection bias.
abstract: OBJECTIVE
  To examine the performance of the disease risk score (DRS) in a cohort study with evidence of policy-induced selection bias.
  
  
  METHODS
  We examined two cohorts of new users of bisphosphonates. Estimates for 1-year hip fracture rates between agents using DRS, exposure propensity scores and traditional multivariable analysis were compared.
  
  
  RESULTS
  The results for the cohort with no evidence of policy-induced selection bias showed little variation across analyses (-4.1-2.0%). Analysis of the cohort with evidence of policy-induced selection bias showed greater variation (-13.5-8.1%), with the greatest difference seen with DRS analyses.
  
  
  CONCLUSIONS
  Our findings suggest that caution may be warranted when using DRS methods in cohort studies with policy-induced selection bias, further research is needed.
authors.affiliation: Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College Street, Toronto, ON, M5S 3M2, Canada.|Institute for Clinical Evaluative Sciences, 2075 Bayview Avenue G1 06, Toronto, ON, M4N 3M5, Canada.|Applied Health Research Centre, Li Ka Shing Knowledge Institute, St Michael's Hospital, 30 Bond St, Toronto, ON, M5B 1W8, Canada.
authors.forename: Mina
authors.initials: M
authors.lastname: Tadrous
authors.affiliation: Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College Street, Toronto, ON, M5S 3M2, Canada.|Institute for Clinical Evaluative Sciences, 2075 Bayview Avenue G1 06, Toronto, ON, M4N 3M5, Canada.|Applied Health Research Centre, Li Ka Shing Knowledge Institute, St Michael's Hospital, 30 Bond St, Toronto, ON, M5B 1W8, Canada.|Institute of Health Policy, Management & Evaluation, University of Toronto, 27 King's College Cir, Toronto, ON, M5S, Canada.
authors.forename: Muhammad M
authors.initials: MM
authors.lastname: Mamdani
authors.affiliation: Institute for Clinical Evaluative Sciences, 2075 Bayview Avenue G1 06, Toronto, ON, M4N 3M5, Canada.|Sunnybrook Research Institute, 2075 Bayview Avenue, Toronto, ON, M4N 3M5T, Canada.
authors.forename: David N
authors.initials: DN
authors.lastname: Juurlink
authors.affiliation: Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College Street, Toronto, ON, M5S 3M2, Canada.|Institute for Clinical Evaluative Sciences, 2075 Bayview Avenue G1 06, Toronto, ON, M4N 3M5, Canada.|Institute of Health Policy, Management & Evaluation, University of Toronto, 27 King's College Cir, Toronto, ON, M5S, Canada.|Toronto Health Economics & Technology Assessment (THETA) Collaborative, Toronto, ON, M5S 3M2, Canada.
authors.forename: Murray D
authors.initials: MD
authors.lastname: Krahn
authors.affiliation: Institute for Clinical Evaluative Sciences, 2075 Bayview Avenue G1 06, Toronto, ON, M4N 3M5, Canada.|Department of Public Health Sciences, Queen's University, 99 University Ave., Kingston, ON K7L 3N6, Canada.
authors.forename: Linda E
authors.initials: LE
authors.lastname: Lévesque
authors.affiliation: Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College Street, Toronto, ON, M5S 3M2, Canada.|Institute for Clinical Evaluative Sciences, 2075 Bayview Avenue G1 06, Toronto, ON, M4N 3M5, Canada.
authors.forename: Suzanne M
authors.initials: SM
authors.lastname: Cadarette
mesh_terms: D050071:Bone Density Conservation Agents; D015331:Cohort Studies; D004164:Diphosphonates; D005260:Female; D006620:Hip Fractures; D006801:Humans; D007349:Insurance, Health, Reimbursement; D015233:Models, Statistical; D009864:Ontario; D016134:Organizational Policy; D010024:Osteoporosis / Q000188:drug therapy; D057766:Policy; D020379:Risk Adjustment; D015983:Selection Bias
chemical_list: D050071:Bone Density Conservation Agents; D004164:Diphosphonates
keywords: cohort studies; confounding factors (epidemiology); data interpretation; multivariate analysis; osteoporosis/epidemiology