title: Access is Not Enough: Characteristics of Physicians Who Treat Medicaid Patients.
abstract: BACKGROUND
  Access to physicians is a major concern for Medicaid programs. However, little is known about relationships between physician participation in Medicaid and the individual-level and practice-level characteristics of physicians.
  
  
  METHODS
  We used the 2011 Massachusetts All Payer Claims Database, containing all commercial and Medicaid claims; we linked with data on physician characteristics. We measured Medicaid participation intensity (fraction of the physician's patient panel with Medicaid) for primary care physicians (PCPs) and medical specialists. We measured influence of physicians within a patient referral network using eigenvector centrality. We used regression models to associate Medicaid intensity with physician individual-level and practice-level characteristics.
  
  
  RESULTS
  About 92.6% of physicians treated at least 1 Medicaid patient, but the median physician's panel contained only 5.7% Medicaid patients. Medicaid intensity was associated with physician training and influence for PCPs and specialists. For medical specialists, a 1 percentage point increase in Medicaid intensity was associated with a lower probability of being board certified (-0.22 percentage points; 95% CI, -0.30, -0.14), lower probability of attending a domestic medical school (-0.14 percentage points; 95% CI, -0.22, -0.05), having attended a less well-ranked domestic medical school (0.23 ranks; 95% CI, 0.15, 0.30), and having slightly less influence in the referral network. PCPs displayed similar results but high Medicaid intensity physicians had substantially less influence in the referral network.
  
  
  CONCLUSIONS
  Medicaid participation intensity shows substantial variation across physicians, indicating limits of binary participation measures. Physicians with more Medicaid patients had characteristics often perceived by patients to be of lower quality.
authors.affiliation: *University of Massachusetts-Amherst School of Public Health and Health Sciences, Amherst †Questrom School of Business, Boston University, Boston ‡National Bureau of Economic Research, Cambridge, MA.
authors.forename: Kimberley H
authors.initials: KH
authors.lastname: Geissler
authors.forename: Benjamin
authors.initials: B
authors.lastname: Lubin
authors.forename: Keith M
authors.initials: KM
authors.lastname: Marzilli Ericson
mesh_terms: D000328:Adult; D002568:Certification / Q000706:statistics & numerical data; D016208:Databases, Factual / Q000706:statistics & numerical data; D005260:Female; D006297:Health Services Accessibility / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008404:Massachusetts; D008484:Medicaid / Q000706:statistics & numerical data*; D008875:Middle Aged; D010342:Patient Acceptance of Health Care; D058007:Physicians, Primary Care / Q000523:psychology / Q000706:statistics & numerical data*; D010818:Practice Patterns, Physicians' / Q000706:statistics & numerical data*; D012017:Referral and Consultation / Q000706:statistics & numerical data; D013038:Specialization / Q000706:statistics & numerical data*; D014481:United States