HWE: Hardy-Weinberg Equilibrium; PB: population based; HB: hospital based; Phet: P value for heterogeneity. *Random-effects model was used when P value for heterogeneity test <0.05; otherwise, fixed-e
With the exception of stored versus source, we restricted the analysis to source water samples. We excluded emergencies from the meta-regression.aPost hoc analysis.bTop tercile of studies versus botto