. Author manuscript; available in PMC: 2018 Mar 1.

Published in final edited form as: Drug Saf. 2017 Mar;40(3):263–272. doi: 10.1007/s40264-016-0490-1

Table 1.

Baseline characteristics of study population, and comparison between patients who were, and were not, exposed to multiple provider prescribing of interacting drugs

Characteristics	Overall (n=88,494)	Exposed (n=1,796)	Unexposed (n=87,368)	p-value^*
Age, mean	45.8	51.9	45.7	<0.0001
Gender (female), n (%)	53,497 (60.5)	1,061 (59.1)	52,436 (60.5)	0.223
Charlson index, mean	0.23	0.73	0.22	<0.0001
Number of providers, mean	6.0	8.4	5.9	<0.0001
Presence of PCP, n (%)	85,032 (96.1)	1,749 (97.4)	83,283 (96.1)	0.005
Care density, mean	19.5	12.1	19.6	<0.0001
Care density, quartile	–	–	–	<0.0001^ˆ
1^st quartile (25^th percentile)	4.7	4.3	4.8	–
2^nd quartile (50^th percentile)	9.3	7.3	9.3	–
3^rd quartile (75^th percentile)	21.0	13.2	21.3	–

The p-value is for the comparison between groups (exposed vs unexposed), and is based on the chi-square test of independence for categorical variables (gender, presence of PCP) and the analysis of variance for continuous variables (age, Charlson index, number of providers, care density);

^ˆ

the p-value based on the analysis of variance across quartiles of care density.