Table 2.
Differential Changes in Annual Specialty Visit Rates from the Pre- to Post-Contract Periods for ACOs vs. Control Group, by ACO Specialty Orientation
| Mean annual rates of specialist visits per beneficiary | |||||
|---|---|---|---|---|---|
| Utilization measure | Unadj. pre-contract mean | Differential change from pre-contract period to 2014 for ACO vs. control group | Difference in differential changes | ||
| 2012 MSSP Cohort | |||||
| All specialist visits, no. | Average Change [95% CI] | p-value | Average Change [95% CI] | p-value | |
| Primary care-oriented ACOs (<13% specialists) |
4.77 | −0.10 [−0.16, −0.04] |
0.002 | −0.05 [−0.13, 0.04] |
0.32 |
| Other ACOs (13-76% specialists) |
5.31 | −0.05 [−0.12, 0.01] |
0.11 | Ref | – |
| New specialist visits, no. | |||||
| Primary care-oriented ACOs (<13% specialists) |
0.746 | −0.037 [−0.051, −0.024] |
<.001 | −0.030 [−0.046, −0.015] |
<.001 |
| Other ACOs (13-76% specialists) |
0.807 | −0.007 [−0.015, 0.001] |
0.09 | Ref | – |
| 2013 MSSP Cohort | |||||
| All specialist visits, no. | |||||
| Primary care-oriented ACOs (<13% specialists) |
5.15 | −0.03 [−0.09, 0.03] |
0.36 | −0.08 [−0.16, 0.00] |
0.05 |
| Other ACOs (13-76% specialists) |
4.95 | 0.05 [0.00, 0.11] |
0.07 | Ref | – |
| New specialist visits, no. | |||||
| Primary care-oriented ACOs (<13% specialists) |
0.777 | −0.009 [−0.019, 0.002] |
0.12 | −0.011 [−0.027, 0.005] |
0.19 |
| Other ACOs (13-76% specialists) |
0.781 | 0.002 [−0.010, 0.014] |
0.73 | Ref | – |
| 2014 MSSP Cohort | |||||
| All specialist visits, no. | |||||
| Primary care-oriented ACOs (<13% specialists) |
4.83 | 0.00 [−0.06, 0.06] |
0.97 | 0.01 [−0.06, 0.08] |
0.84 |
| Other ACOs (13-76% specialists) |
5.15 | −0.01 [−0.05, 0.03] |
0.653 | Ref | – |
| New specialist visits, no. | |||||
| Primary care-oriented ACOs (<13% specialists) |
0.749 | −0.023 [−0.032, −0.013] |
<.001 | −0.027 [−0.039, −0.014] |
<.001 |
| Other ACOs (13-76% specialists) |
0.798 | 0.004 [−0.004, 0.012] |
0.31 | Ref | – |
Abbreviations: Accountable care organization (ACO), confidence interval (CI), hospital referral region (HRR), Medicare Shared Savings Program (MSSP)
Pre-contract means are shown for all groups (2010-2011 for the 2012 entry cohort, 2010-2012 for the 2013 cohort, and 2010-2013 for the 2014 cohort). Differences in ACO vs. control group trends estimated using linear regression adjusting for all characteristics in Table 1, HRR by year and ACO fixed effects and year fixed effects. All standard errors are clustered at the ACO organization level for ACO-assigned beneficiaries and at the HRR level for the control group. Difference in differential trends estimate the difference-in-difference estimates between primary-care oriented and specialty-oriented ACOs.