Article Figures & Data
Figures
- Figure 1
Study population flow diagram.
Tables
Characteristic Selected, No. (%)(n = 13,219) Not Selected, No. (%)(n = 21,630) P Valuea Sex .56 Female 7,639 (57.8) 12,431 (57.5) Male 5,580 (42.2) 9,199 (42.5) Age-group, yb <.001 19–29 3,529 (26.7) 5,877 (27.2) 30–39 3,212 (24.3) 4,831 (22.3) 40–49 3,300 (25.0) 5,720 (26.4) 50–59 2,574 (19.5) 4,209 (19.5) 60–64 604 (4.6) 993 (4.6) Race/ethnicity .004 Hispanic, any race 1,750 (13.2) 2,579 (11.9) Non-Hispanic, white 8,635 (65.3) 14,295 (66.1) Non-Hispanic, other 1,495 (11.3) 2,519 (11.7) Unknown 1,339 (10.1) 2,237 (10.3) Average federal poverty levelc .36 <100% 8,215 (62.2) 13,564 (62.7) ≥100% 3,598 (27.2) 5,736 (26.5) Missing/unknown 1,406 (10.6) 2,330 (10.8) Number of chronic conditionsd .25 Missing/unknown 4,240 (32.1) 6,758 (31.2) 0 7,075 (53.5) 11,547 (53.4) 1 1,128 (8.5) 1,989 (9.2) 2 509 (3.9) 859 (4.0) 3 221 (1.7) 402 (1.9) 4 43 (0.3) 69 (0.3) 5 3 (0.02) 6 (0.03) Note: Oregon OCHIN patients selected to apply for health insurance coverage via Oregon Experiment compared with those patients not selected to apply.
↵a P values for χ2 test.
↵b Mean (SD) age was 39.3 (12.1) years for selected patients vs 39.4 (12.2) years for nonselected patients; 2-sided Wilcoxon rank sum test P =.50.
↵c Values ≥1,000% of the federal poverty level (seen in less than 1% of patients) were set to missing.
↵d Diagnosed before selection date; among asthma, coronary artery disease, diabetes, dyslipidemia, and hypertension. Missing/unknown indicates that patient had no preselection date encounters from which to assess chronic condition diagnoses.
- Table 2
Intent-to-Treat Outcome Rates by Selection Group (Selected n = 13,219; Not Selected n = 21,630)
Unadjusted Outcome in Postselection Period Rate per 1,000 Patients/Month (SE) Absolute Difference in Rate Rate Ratio (95% CI) Adjusted Rate Ratio (95% CI) Total primary care office visitsa Selectedb 235 (12) −1 1.00 (0.93–1.08) 1.01 (0.94–1.09) Not selected (ref) 236 (17) – 1.00 1.00 Total behavioral/mental health visitsc Selected 201 (28) −31d 0.87 (0.79–0.94)d 0.89 (0.81–0.99)d Not selected (ref) 232 (29) – 1.00 1.00 Total laboratory testse Selected 342 (28) −13 0.96 (0.88–1.05) 0.97 (0.89–1.05) Not selected (ref) 355 (39) – 1.00 1.00 Total referralsf Selected 45 (9) +5 1.14 (0.95–1.37) 1.18 (1.02–1.35)d Not selected (ref) 40 (6) – 1.00 1.00 Total immunizationsg Selected 57 (4) −2 0.97 (0.93–1.01) 0.98 (0.94–1.03) Not selected (ref) 59 (4) – 1.00 1.00 Total imaging studiesh Selected 43 (3) +2 1.06 (0.99–1.13) 1.08 (1.01–1.16)d Not selected (ref) 41 (2) – 1.00 1.00 CHC = community health center; CPT = Current Procedural Terminology; EHR = electronic health record; HCPCS = Healthcare Common Procedure Coding System; ref = reference group; SE = standard error.
Notes: (1) Rates are zero-inflated Poisson regression estimates. Adjusted estimates controlled for categorical age and race/ethnicity as these variables differed significantly between the selection groups at baseline. (2) All models accounted for clustering of patients by primary CHC through a robust sandwich variance estimator. (3) Postselection period was the 36 months after an applicant was notified of selection to apply for insurance coverage (the selection date) through the Oregon Experiment or, for those not selected, a randomly assigned selection date based on the distribution of selection dates for the selected group. (4) SE denotes robust standard error estimate of the use rate that accounts for clustering of patients within primary CHC.
↵a Face-to-face office visits in a primary care setting and/or with a primary care clinician.
↵b Oregon OCHIN patients selected to apply for health insurance coverage via the Oregon Experiment vs not selected.
↵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 Statistically significant difference compared with reference group.
↵e CPT and HCPCS codes grouped as laboratory tests in the EHR.
↵f CPT and HCPCS codes grouped as referrals in the EHR.
↵g CPT and HCPCS codes grouped as immunizations in the EHR.
↵h CPT and HCPCS codes grouped as imaging studies in the EHR.
- 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 Period Rate per 1,000 Patients/Month (SE) Absolute Difference in Rate Rate Ratio (95% CI) Total primary care office visitsa Medicaid coverage 282 (21) +81b 1.39 (1.16–1.66)b No Medicaid coverage (ref) 201 (15) – 1.00 Total behavioral/mental health visitsc Medicaid coverage 183 (37) −13 0.93 (0.66–1.32) No Medicaid coverage (ref) 196 (28) – 1.00 Total laboratory testsd Medicaid coverage 436 (43) +94b 1.27 (1.05–1.55)b No Medicaid coverage (ref) 342 (38) – 1.00 Total referralse Medicaid coverage 45 (14) +17b 1.58 (1.10–2.28)b No Medicaid coverage (ref) 28 (5) – 1.00 Total immunizationsf Medicaid coverage 57 (6) +1 1.03 (0.87–1.21) No Medicaid coverage (ref) 56 (4) – 1.00 Total imaging studiesg Medicaid coverage 45 (5) +11b 1.33 (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.
Supplemental Tables 1-2
Supplemental Table 1. Table 1. Demographic Characteristics of Effect of Treatment on the Treated Study Sample by Selection Status (N=24,705); Supplemental Table 2. Effect of Treatment On the Treated Outcome Rates by Selection Group (Selected and Gained Insurance: n=5,267; Not Selected and Did Not Gain Insurance: n=19,438)
Files in this Data Supplement:
- Supplemental data: Tables 1-2 - PDF file
The Article in Brief
Community Health Center Use After Oregon's Randomized Medicaid Experiment
Steffani R. Bailey , and colleagues
Background Will Community Health Centers (CHCs) experience increased demand from patients who gain health care coverage through the Affordable Care Act's Medicaid expansion? This study explores that question by examining primary care use over a three-year period in a population of low-income adult CHC patients who gained coverage when Oregon expanded its Medicaid program in 2008.
What This Study Found Analysis of data on 34,849 patients showed that Medicaid coverage significantly increased the rate of primary care visits, laboratory tests, referrals and imaging. Specifically, the number of primary care office visits per month was 282 per 1,000 Medicaid-covered patients, compared with 201 for patients without such coverage. In the 3-year follow-up period, Medicaid coverage led to a 58 percent higher rate of referrals, 27 percent higher rate of orders for laboratory tests and a 33 percent higher imaging rate.
Implications
- ACA insurance expansions could lead to increased demand for services from CHCs and other primary care settings. According to the authors, it will be important to ensure that the health care system can support increasing demands by providing more resources to CHCs and other primary care settings.
