The confounding factors for the potential sources of heterogeneity studied by meta-regression.

Abbreviations: Year: publication year; Region 1: northern China; Region 2: southern China; Case size: CAD group sample size; Con size: the total number of control group; Tot size: total sample size; RR: the ratio of case size to control size; LnOR: the natural logarithm of odds ratio for the 4G allelic distribution frequency of PAI-1 gene 4G/5G polymorphism between CAD and control groups.