. Author manuscript; available in PMC: 2011 Aug 23.

Published in final edited form as: Curr Opin Rheumatol. 2010 Jul;22(4):397–403. doi: 10.1097/BOR.0b013e32833ac7fe

Table 1.

Calculating compliance and persistence under various assumptions for the sample patient depicted in Figure 2

	Compliance (Proportion of Days Covered)		%	Persistence (60 day permissible gap)
	No. days drug supplied (numerator)	No. days observed (denominator)	%	No. days in largest gap	No. days persisted^c
Truth (Figure 2A)	120	180	66.7	(46+7)=53	180
Claims data “raw” (Figure 2B)
ignoring days in hospital	90	180	50.0	(53+30)=83	67
subtract days in hospital (n=12)^a	90	168	53.5	(83−12)=71	67
100% covered in hospital (n=12)^b	102	180	56.7	46	180
50% days supplied grace period (Figure 2C)
ignoring days in hospital	112	180	62.0	(46−15+7+30)=68	82
subtract days in hospital (n=12)^a	112	168	66.7	(68−12)=56	180
100% covered in hospital (n=12)^b	124	180	68.9	(46−15)=31	180

Proportion of days covered (PDC)=(number of days of drug supplied in the observation period/number of days in the observation period), capped at 1 or 100%.

PDC: corrected for immeasurable time in hospital by subtracting 12 days from denominator; persistence: subtract days in hospital (12 days) from gap length

PDC: corrected for immeasurable time in hospital by adding 12 days to numerator; persistence: subtract days in hospital (12 days) from gap length

defined by the number of days covered by drug before a gap of more than 60 days