Table 1.

Summary of Prior Literature on Medication Inclusion Criteria for Identifying Prevalent User Cohorts in Copay Change Evaluations

	Characteristics of Preperiod Inclusion Criteria of Medication Use
Author (Year)	Preperiod Duration (Months)	Number of Preperiod Intervals	Overlapping Intervals?	Number of Fills per Interval	Each Preperiod Interval Length
Maciejewski et al. (2010a)	12	2	No	1+, 1+	3, 9
Doshi et al. (2009)	24	2	Yes	1+, 1+	3, 24
Yin et al. (2008)	24	1	No	1+	24
Blais et al. (#b3000)	70	1	No	1+	70
Roblin et al. (2005)	6	1	No	4+	6