Table 3

Estimated Effect of Gaining Medicaid Coverage on Use Outcomes Among Oregon OCHIN Patients Who Participated in the Oregon Experiment (N = 34,849)

Outcome in Postselection PeriodRate per 1,000 Patients/Month (SE)Absolute Difference in RateRate Ratio (95% CI)
Total primary care office visitsa
 Medicaid coverage282 (21)+81b1.39 (1.16–1.66)b
 No Medicaid coverage (ref)201 (15)1.00
Total behavioral/mental health visitsc
 Medicaid coverage183 (37)−130.93 (0.66–1.32)
 No Medicaid coverage (ref)196 (28)1.00
Total laboratory testsd
 Medicaid coverage436 (43)+94b1.27 (1.05–1.55)b
 No Medicaid coverage (ref)342 (38)1.00
Total referralse
 Medicaid coverage45 (14)+17b1.58 (1.10–2.28)b
 No Medicaid coverage (ref)28 (5)1.00
Total immunizationsf
 Medicaid coverage57 (6)+11.03 (0.87–1.21)
 No Medicaid coverage (ref)56 (4)1.00
Total imaging studiesg
 Medicaid coverage45 (5)+11b1.33 (1.07–1.64)b
 No Medicaid coverage (ref)34 (2)1.00
  • Acronyms are as shown in Table 2 footnote.

  • Notes: (1) Rates calculated using the 2-stage residual inclusion instrumental variable approach. Models adjusted for categorical age and race/ethnicity as these variables differed significantly between selection groups at baseline. (2) SEs were estimated with 2,000 bootstrap replicates clustered by primary CHC. (3) Postselection period was the 36 months after an applicant was notified of selection to apply for health insurance coverage (the selection date) via the Oregon Experiment or, for those not selected, a randomly assigned selection date based on the distribution of selection dates for the selected group.

  • a Face-to-face office visits in a primary care setting and/or with a primary care clinician.

  • b Statistically significant difference compared with reference group.

  • c Face-to-face encounters designated as behavioral or mental health in the EHR; limited to 11,571 patients seen at 1 or more of the 33 clinics with the behavioral/mental health visit indicator.

  • d CPT and HCPCS codes grouped as laboratory tests in the EHR.

  • e CPT and HCPCS codes grouped as referrals in the EHR.

  • f CPT and HCPCS codes grouped as immunizations in the EHR.

  • g CPT and HCPCS codes grouped as imaging in the EHR.