title: Unhealthy competition: consequences of health plan choice in California Medicaid.
abstract: OBJECTIVE
  We compared the quality of care received by managed care Medicaid beneficiaries in counties with a choice of health plans and counties with no choice.
  
  
  METHODS
  This cross-sectional study among California Medicaid beneficiaries was conducted during 2002. We used a multivariate Poisson model to calculate adjusted rates of hospital admissions for ambulatory care-sensitive conditions by duration of plan enrollment.
  
  
  RESULTS
  Among beneficiaries with continuous Medicaid coverage, the percentage with 12 months of continuous enrollment in a health plan was significantly lower in counties with a choice of plans than in counties with no choice (79.2% vs 95.2%; P < .001). Annual ambulatory care-sensitive admission rates adjusted for age, gender, and race/ethnicity were significantly higher among beneficiaries living in counties with a choice of plans (6.58 admissions per 1000 beneficiaries; 95% confidence interval [CI] = 6.57, 6.58) than among those in counties with no choice (6.27 per 1000; 95% CI = 6.27, 6.28).
  
  
  CONCLUSIONS
  Potential benefits of health plan choice may be undermined by transaction costs of delayed enrollment, which may increase the probability of hospitalization for ambulatory care-sensitive conditions.
authors.affiliation: Division of General Internal Medicine, San Francisco General Hospital, San Francisco, CA, USA. c.millett@imperial.ac.uk
authors.forename: Christopher
authors.initials: C
authors.lastname: Millett
authors.forename: Arpita
authors.initials: A
authors.lastname: Chattopadhyay
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Bindman
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000553:Ambulatory Care / Q000706:statistics & numerical data; D002140:California; D002648:Child; D002675:Child, Preschool; D002755:Choice Behavior; D016536:Competitive Medical Plans / Q000706:statistics & numerical data*; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D007223:Infant; D008297:Male; D008484:Medicaid / Q000458:organization & administration / Q000706:statistics & numerical data*; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D016012:Poisson Distribution; D011787:Quality of Health Care / Q000458:organization & administration / Q000706:statistics & numerical data*; D012737:Sex Factors; D013997:Time Factors; D014481:United States; D055815:Young Adult