Table 3.

Segmented Regression Analysis: Changes in the Difference Between the Intervention and the Comparison Groups

Prescribing metric	Parameter	Description	Parameter estimate	Standard error	t-statistic	P value
Proportion of patients with diabetes who received metformin	β0	Intercept: baseline group difference level	–0.0601	0.0027	–22.02	<.0001
	β1	Preintervention slope: trend of group difference before intervention	0.0040	0.0004	10.59	<.0001
	β2	Change in group difference level immediately after intervention	–0.0110	0.0039	–2.85	.0102
	β3	Change in group difference trend over time after intervention	–0.0040	0.0005	–8.13	<.0001
Proportion of patients with diabetes and hypertension who received an ACE inhibitor or an ARB	β0	Intercept: baseline group difference level	–0.0011	0.0109	–0.10	.9220
	β1	Preintervention slope: trend of group difference before intervention	0.0005	0.0014	0.40	.6945
	β2	Change in group difference level immediately after intervention	–0.0029	0.0090	–0.32	.7519
	β3	Change in group difference trend over time after intervention	–0.0014	0.0023	–0.62	.5426
Proportion of patients with diabetes who received a statin	β0	Intercept: baseline group difference level	–0.0067	0.0059	–1.14	.2679
	β1	Preintervention slope: trend of group difference before intervention	–0.0001	0.0008	–0.12	.9088
	β2	Change in group difference level immediately after intervention	–0.0145	0.0078	–1.85	.0788
	β3	Change in group difference trend over time after intervention	0.0006	0.0011	0.50	.6239
Proportion of sulfonylurea prescriptions for long-acting agents	β0	Intercept: baseline group difference level	0.0209	0.0042	4.95	<.0001
	β1	Preintervention slope: trend of group difference before intervention	–0.0003	0.0006	–0.55	.5890
	β2	Change in group difference level immediately after intervention	–0.0147	0.0058	–2.55	.0197
	β3	Change in group difference trend over time after intervention	–0.0012	0.0008	–1.46	.1614

ACE indicates angiotensin-converting enzyme; ARB, angiotensin receptor blocker.