title: Estimating the effect of treatment rate changes when treatment benefits are heterogeneous: antibiotics and otitis media.
abstract: OBJECTIVE
  Contrast methods to assess the health effects of a treatment rate change when treatment benefits are heterogeneous across patients. Antibiotic prescribing for children with otitis media (OM) in Iowa Medicaid is the empirical example.
  
  
  METHODS
  Instrumental variable (IV) and linear probability model (LPM) are used to estimate the effect of antibiotic treatments on cure probabilities for children with OM in Iowa Medicaid. Local area physician supply per capita is the instrument in the IV models. Estimates are contrasted in terms of their ability to make inferences for patients whose treatment choices may be affected by a change in population treatment rates.
  
  
  RESULTS
  The instrument was positively related to the probability of being prescribed an antibiotic. LPM estimates showed a positive effect of antibiotics on OM patient cure probability while IV estimates showed no relationship between antibiotics and patient cure probability.
  
  
  CONCLUSIONS
  Linear probability model estimation yields the average effects of the treatment on patients that were treated. IV estimation yields the average effects for patients whose treatment choices were affected by the instrument. As antibiotic treatment effects are heterogeneous across OM patients, our estimates from these approaches are aligned with clinical evidence and theory. The average estimate for treated patients (higher severity) from the LPM model is greater than estimates for patients whose treatment choices are affected by the instrument (lower severity) from the IV models. Based on our IV estimates it appears that lowering antibiotic use in OM patients in Iowa Medicaid did not result in lost cures.
authors.affiliation: Health Research Consultant, Health Dialog Analytic Solutions, Portland, ME, USA.
authors.forename: Tae-Ryong
authors.initials: TR
authors.lastname: Park
authors.forename: John M
authors.initials: JM
authors.lastname: Brooks
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Chrischilles
authors.forename: George
authors.initials: G
authors.lastname: Bergus
mesh_terms: D000900:Anti-Bacterial Agents / Q000191:economics* / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D005260:Female; D017048:Health Care Costs; D006801:Humans; D007223:Infant; D007484:Iowa; D008297:Male; D008484:Medicaid / Q000191:economics / Q000592:standards; D008485:Medical Audit; D018803:Models, Economic; D015233:Models, Statistical; D010033:Otitis Media / Q000188:drug therapy / Q000191:economics*; D017063:Outcome Assessment, Health Care / Q000191:economics* / Q000379:methods; D010818:Practice Patterns, Physicians'; D014481:United States
chemical_list: D000900:Anti-Bacterial Agents