title: Measuring patient safety in ambulatory care: potential for identifying medical group drug-drug interaction rates using claims data.
abstract: OBJECTIVE
  To evaluate the feasibility of using health-plan administrative data to measure potential drug-drug interaction (DDI) rates in the ambulatory setting at the medical-group level and to assess the potential use of DDI rates in performance measurement, quality improvement, and research in patient safety.
  
  
  METHODS
  We combined administrative and pharmacy claims data from 2 large health plans to calculate the rates at which member users of selected chronic medications were potentially exposed to a second drug known to pose a risk of harmful interactions.
  
  
  METHODS
  We divided 44 medication combinations with risk of adverse interactions into those with DDIs of moderate/severe clinical significance and those with DDIs of mild significance. We then calculated yearly rates of potential DDIs in continuously enrolled members aged 19 and older from 1998 through 2001. Rates were calculated for all members, overall base-medication users, and, individual medical groups responsible for their care.
  
  
  RESULTS
  The analytic data set included 756 047 patient-years of data and 110 to 123 medical groups per year. During the 4-year interval, one or more unique potential DDIs occurred in 6.2% to 6.7% of base-drug users and 2.0% to 2.3% of all adult health-plan members per year. Medical-group mean user rates were slightly lower (5.33%-5.81%), with wide variance (SD = 2.6%-3.1%) and high stability over time.
  
  
  CONCLUSIONS
  Potential DDI rates calculated from health-plan data have promise for measurement in patient medication safety. This readily available and inexpensive evaluation tool has potential for monitoring, improvement, and research purposes if further studies validate their relationship to actual adverse events.
authors.affiliation: HealthPartners Research Foundation, Minneapolis, MN 55440-1524, USA. leif.i.solberg@healthpartners.com
authors.forename: Leif I
authors.initials: LI
authors.lastname: Solberg
authors.forename: Judith S
authors.initials: JS
authors.lastname: Hurley
authors.forename: Melissa H
authors.initials: MH
authors.lastname: Roberts
authors.forename: Winnie W
authors.initials: WW
authors.lastname: Nelson
authors.forename: Floyd J
authors.initials: FJ
authors.lastname: Frost
authors.forename: A Lauren
authors.initials: AL
authors.lastname: Crain
authors.forename: Margaret J
authors.initials: MJ
authors.lastname: Gunter
authors.forename: Linda R
authors.initials: LR
authors.lastname: Young
mesh_terms: D000328:Adult; D016907:Adverse Drug Reaction Reporting Systems; D000368:Aged; D000553:Ambulatory Care / Q000592:standards*; D004347:Drug Interactions; D017723:Drug Utilization Review / Q000379:methods*; D005260:Female; D006123:Group Practice / Q000592:standards / Q000706:statistics & numerical data; D006279:Health Maintenance Organizations / Q000592:standards* / Q000706:statistics & numerical data; D006801:Humans; D007345:Insurance Claim Review; D008297:Male; D008508:Medication Errors / Q000706:statistics & numerical data*; D008875:Middle Aged; D008910:Minnesota; D009516:New Mexico; D019338:Polypharmacy; D018570:Risk Assessment / Q000379:methods; D012449:Safety