(c) Q1011E

	N a	QE versus QQ	P b	EE versus QQ	P b	EE versus QQ/QE	P b	N a	QE/EE versus QQ	P b
Total	4	1.59 (0.91–2.81)	0.201	2.20 (0.40–12.07)	0.863	2.14 (0.39–11.75)	0.859	4	1.59 (0.91–2.81)	0.201

^aNumber of studies

^b P value of Q test for heterogeneity

SOC: Source of controls, HB: hospital-based control group, and PB: population-based control group.