Table 2.

Interrupted time series with comparator group segmented regression analysis: estimates of the difference between treatment (ACC assignees) vs. comparator (other large practice assignees) on changes in monthly expenditure and utilization time trends associated with ACC implementation

		Post-Period (vs. Pre-Period)
Enrollment	Outcome	Level1	P-Value	Slope2	P-Value
TANF	Plan Expenditures	−$6.70	0.84	$2.50	0.32
(N=410,151 person-months; 25,092 people)	Any Hospitalization	0.01%	0.96	0.01%	0.26
	Any ED Visit	0.70%	0.06	0.01%	0.82
SSI (Without Medicare)	Plan Expenditures	−$47.87	0.34	−$0.16	0.96
(N=457,667 person-months; 23,802 people)	Any Hospitalization	−0.08%	0.76	0.00%	0.96
	Any ED Visit	0.02%	0.96	0.04%	0.19
Expansion	Plan Expenditures	$65.18	0.28	$16.20	0.13
(N=214,339 person-months; 17,526 people)	Any Hospitalization	−0.32%	0.31	−0.01%	0.89
	Any ED Visit	0.99%	0.10	0.08%	0.39
UHC Medicare-Medicaid Dual	Plan Expenditures	$66.11	0.31	−$0.01	1.00
(N=118,301 person-months; 6,332 people)	Any Hospitalization	0.65%	0.07	−0.00%	0.90
	Any ED Visit	0.18%	0.75	−0.04%	0.22

Notes: Linear regression used for expenditures; logistic regression used for utilization outcomes. Sample is person-months eligible from 2010–2016.

^*denotes significance at p < .05. Regression covariates of interest were study Group (treatment [ACC assignees] vs. comparator [other large practice assignees]); a linear monthly time trend counting months before and after ACC activation (real or proxy; ACC activation defined as time zero), indicators and splines for the post period (months 0 and after); and the interactions between these variables and Group. Other covariates included sex, age group, race, language, 17 comorbidity indicators (arthritis, asthma, atrial fibrillation, autism, cancer, chronic obstructive pulmonary disease, congestive heart failure, dementia, depression, HIV, hyperlipidemia, liver disease, myocardial infarction, osteoporosis, schizophrenia, stroke, and substance abuse), state-by-year fixed effects, an indicator for whether a state had adopted the Medicaid Expansion in the given month, and seasonality. Repeated measures adjusted for using generalized estimating equations (GEE), clustering by practice ID.

^1.Difference between treatment vs. comparator in the discontinuity (change in level) for the post period, measured using marginal effects post-estimation of the interaction between Group & an indicator variable for the post period.

^2.Difference between treatment vs. comparator in the change in slope for the post period, measured using marginal effects post-estimation of the interaction between Group & a spline variable for the post period.