Table 2.

Summary of adherence rate and heterogeneity findings

Outcomes	No of studies	No of participants	Adherence, % (95% CIs)	Heterogeneity		Test for overall effect
				P-value	I2 (%)	Z	P-value
Overall	22	1 37 699	47 (42 to 52)	0.000	99.7	18.66	0.000
Measurement methods
Prescription claims	16	1 37 134	42 (37 to 47)	0.000	99.8	15.61	0.000
Pill count	1	132	71 (63 to 79)	–	–	18.06	0.000
Self-report	3	376	66 (50 to 81)	0.001	86.3	8.40	0.000
Interview	3	148	63 (42 to 83)	0.003	82.9	6.09	0.000
Publication year
2010	6	41 766	34 (26 to 43)	0.000	99.7	8.22	0.000
2010–	16	95 923	53 (47 to 60)	0.000	99.7	15.95	0.000
Country of origin
USA	11	59 888	40 (33 to 47)	0.000	99.6	11.82	0.000
Oceania	2	788	78 (75 to 81)	0.860	0	52.97	0.000
Europe	5	69 076	44 (40 to 49)	0.000	98.0	19.62	0.000
Asia	4	7947	56 (17 to 96)	0.000	99.4	2.81	0.000
Data sources
Database	14	13 700	40 (34 to 45)	0.000	99.8	13.48	0.000
Non-database	8	699	65 (54 to 75)	0.000	89.2	11.81	0.000
Representativeness
Multiple sites	17	1 37 319	44 (39 to 50)	0.000	99.8	15.79	0.000
Single site	5	380	60 (43 to 76)	0.000	92.1	7.04	0.000
Sample size
≥200	15	1 37 251	42 (36 to 48)	0.000	99.8	14.55	0.000
<200	7	448	62 (48 to 75)	0.000	89.3	9.12	0.000
Cut-point
≥80%	18	1 37 517	45 (40 to 51)	0.000	99.7	16.70	0.000
≥75%	1	19	62 (52 to 72)	0.004	77.8	7.54	0.000
NS	4	182	60 (45 to 76)	–	–	12.16	0.000
Quality
≥3 points	15	1 37 251	42 (36 to 48)	0.000	99.8	14.55	0.000
<3 points	7	448	62 (48 to 75)	0.000	89.3	9.12	0.000

NS, not stated.