Characteristics of eligible studies included in the meta-analysis.

PB: population-based; HB: hospital-based; HWE: Hardy-Winberg equilibrium. Genotyping method: PCR-RFLP, polymerase chain reaction-restriction fragment length polymorphism; MassARRAY: genotyping was performed using the Sequenom MassARRAY iPLEXTM platform2. MassARRAY Workstation version 3.3 software was used to process and analyze iPLEX SpectroCHIP bioarrays; PCR-HRM, PCR cycling and high resolution melting analysis was performed on the Rotor-Gene 6000TM. APEX: polymorphism was analyzed together for a given sample by a microarray technique based on the arrayed primer extension principle.