Table 2.

Naïve Model and Two-stage Residual Inclusion (2SRI) Model Results for Any Drug Use and PDC among Users

		Naïve Model			2SRI Model
Drug Class	N	(a) ATE for PDP Enrollment	[95% CI]		(b) LATE for PDP Enrollment	[95% CI]
Any drug use
Oral antidiabetics	111,290	−0.041	−0.0548	−0.0281	−0.1069	−0.2246	0.0109
ACE-inhibitors/ARBs	111,290	−0.0187	−0.0314	−0.0061	−0.0489	−0.1676	0.0699
Antihyperlipidemics	111,290	−0.0068	−0.0200	0.0064	−0.0574	−0.1751	0.0602
Proportion of days covered among users

Drug class	N	(c) ATE for PDP Enrollment	[95% CI]		(d) LATE for PDP Enrollment	[95% CI]
Oral antidiabetics	69,396	0.0348	0.0264	0.0432	0.1161	0.0205	0.2116
ACE-inhibitors/ARBs	77,110	0.0468	0.0379	0.0558	0.1314	0.0338	0.2291
Antihyperlipidemics	73,601	0.0465	0.0372	0.0558	−0.0144	−0.1089	0.0801

Note. These results are adjusted for the variables listed in Table 1. The instrumental variable is the county-level MA penetration in year 2005. LATE and ATE are calculated using Stata “mfx” command for naïve models, and Terza, Basu, and Rathouz (2008) definition for 2SRI models. The preferred estimates are the naïve model estimates for any drug use (in all three drug classes) and PDC of antihyperlipidemics, but the 2SRI estimates for the PDC of oral antidiabetics and antihyperlipidemics (see Results section for further discussion).

ATE, average treatment effect; LATE, local average treatment effect.