The impact of generic-only drug benefits on patients' use of inhaled corticosteroids in a Medicare population with asthma

Table 5 Adjusted change in annual ICS days-of-supply for lower and higher-risk asthma patients: restricted vs. unrestricted coverage

	Baseline ICS Days-of-Supply (2003)		Change in ICS Days-of-Supply from 2003 to 2004		Change in ICS Days-of-Supply from 2003 to 2004: Restricted vs. Unrestricted Coverage (Difference-in-difference)
	Restricted Coverage	Unrestricted Coverage	Restricted Coverage	Unrestricted Coverage	Restricted vs. Unrestricted	(95% CI)	p-value
Lower-risk asthma patients (n = 1,584)	181.20	197.70	-30.46	-14.90	-15.56	(-25.77, -5.34)	0.003
Higher-risk asthma patients (n = 218)	192.79	227.58	-28.97	-14.00	-14.97	(-41.38, 11.44)	0.265

Notes: Each row represents a separate OLS regression model. We classified those with a high-risk asthma flag as higher-risk and those with no high-risk flag as lower-risk asthma patients (please see Table 3). We calculated mean changes in ICS days-of-supply for each coverage group by using the lincom command in Stata 8.2 and the mean levels of the covariables. The baseline ICS days-of-supply presents the unadjusted mean days-of-supply in each group in 2003.

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