title: How price responsive is the demand for specialty care?
abstract: OBJECTIVE
  Outpatient visit co-payments have increased in recent years. We estimate the patient response to a price change for specialty care, based on a co-payment increase from $15 to $50 per visit for veterans with hypertension.
  
  
  METHODS
  A retrospective cohort of veterans required to pay co-payments was compared with veterans exempt from co-payments whose nonequivalence was reduced via propensity score matching. Specialty care expenditures in 2000-2003 were estimated via a two-part mixed model to account for the correlation of the use and level outcomes over time, and results from this correlated two-part model were compared with an uncorrelated two-part model and a correlated random intercept two-part mixed model.
  
  
  RESULTS
  A $35 specialty visit co-payment increase had no impact on the likelihood of seeking specialty care but induced lower specialty expenditures over time among users who were required to pay co-payments. The log ratio of price responsiveness (semi-elasticity) for specialty care increased from -0.25 to -0.31 after the co-payment increase. Estimates were similar across the three models.
  
  
  CONCLUSIONS
  A significant increase in specialty visit co-payments reduced specialty expenditures among patients obtaining medications at the Veterans Affairs medical centers. Longitudinal expenditure analysis may be improved using recent advances in two-part model methods.
authors.affiliation: Durham VA Medical Center, Center for Health Services Research in Primary Care, Durham, NC, USA. mlm34@duke.edu
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Maciejewski
authors.forename: Chuan-Fen
authors.initials: CF
authors.lastname: Liu
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Kavee
authors.forename: Maren K
authors.initials: MK
authors.lastname: Olsen
mesh_terms: D000368:Aged; D017047:Cost Sharing / Q000191:economics*; D003365:Costs and Cost Analysis / Q000191:economics*; D005260:Female; D006297:Health Services Accessibility / Q000191:economics*; D006801:Humans; D006973:Hypertension / Q000628:therapy; D008137:Longitudinal Studies; D008297:Male; D008511:Medicine / Q000706:statistics & numerical data*; D008875:Middle Aged; D017059:Models, Econometric; D012189:Retrospective Studies; D012959:Socioeconomic Factors; D014481:United States; D014493:United States Department of Veterans Affairs / Q000706:statistics & numerical data