title: Evaluating the introduction of a computerized prior-authorization system on the completeness of drug exposure data.
abstract: OBJECTIVE
  Administrative databases that only capture records for benefit-approved prescriptions may underestimate exposure because they do not capture non-benefit prescriptions. Using a natural experiment, we illustrate the impact of automating a prior-authorization policy on the completeness of drug exposure.
  
  
  METHODS
  Using Saskatchewan (Canada) databases, weekly counts of benefit-approved and total prescription records in 2006 for new users of antidiabetic agents were examined across four categories: thiazolidinediones (TZDs), metformin, glyburide, and insulin. On July 1, 2006, Saskatchewan's public drug plan implemented an automated, online-adjudicated, prior-authorization process for TZDs; previously, prior approval was paper based. No such policy changes occurred for other drugs. We estimated the effect of this policy change on drug exposure using interrupted time-series analyses.
  
  
  RESULTS
  We examined 223 552 prescription records: 19% were for TZDs, 48% for metformin, 20% for glyburide, and 13% for insulin. Prior to automation, there were, on average, 571 benefit-approved TZD records per week; however, the number of benefit-approved TZD records increased immediately after the automated process was introduced by 240 prescriptions per week (95% CI 200-280, p < 0.001). The average proportion of TZD benefit-approved records was 73% before and increased to 93% immediately following policy change (20% absolute change, 95% CI 18.7-20.4%). No changes were observed for metformin, glyburide, or insulin (p > 0.1 for all).
  
  
  CONCLUSIONS
  Automating prior authorization for TZDs immediately increased the proportion of captured TZD records, suggesting in our study that one-fifth of TZD exposure was previously misclassified. If replicable, this indicates that even subtle changes in reimbursement policy may affect the validity of drug exposure data.
authors.affiliation: School of Pharmacy, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada, A1B 3V6. jgamble@mun.ca
authors.forename: John-Michael
authors.initials: JM
authors.lastname: Gamble
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Johnson
authors.forename: Sumit R
authors.initials: SR
authors.lastname: Majumdar
authors.forename: Finlay A
authors.initials: FA
authors.lastname: McAlister
authors.forename: Scot H
authors.initials: SH
authors.lastname: Simpson
authors.forename: Dean T
authors.initials: DT
authors.lastname: Eurich
mesh_terms: D000328:Adult; D016208:Databases, Factual / Q000706:statistics & numerical data*; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D019458:Insurance Coverage / Q000706:statistics & numerical data; D007356:Insurance, Pharmaceutical Services / Q000706:statistics & numerical data*; D016347:Medical Records Systems, Computerized; D016134:Organizational Policy; D017891:Pharmacoepidemiology; D012051:Reimbursement Mechanisms; D012525:Saskatchewan; D013997:Time Factors
chemical_list: D007004:Hypoglycemic Agents