Table 2.

Meta-regression analysis of potential source of heterogeneity

Heterogeneity Factor	Coefficient	Standard Error	T-test	P-value	95%CI
Year of publication	0.335	0.812	0.41	0.689	-1.501–2.171
Country: Asia and Europe	0.999	1.004	0.99	0.346	-1.273–3.270
Study design: Non-case–control design	1.032	0.991	1.04	0.325	-1.210–3.273
Sample size	0.132	0.909	0.15	0.888	-1.925–2.189
Disease severity	0.093	1.054	0.09	0.932	-2.292–2.478