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Table 1 Scale for quality assessment

From: Current evidences on XPC polymorphisms and gastric cancer susceptibility: a meta-analysis

Criteria Score
Representativeness of cases  
 Selected from cancer registry or multiple cancer center sites 2
 Selected from oncology department or cancer institute 1
 Selected without clearly defined sampling frame or with extensive inclusion/exclusion criteria 0
Source of controls  
 Population or community based 2
 Both population-based and hospital-based/healthy volunteers/blood donors 1.5
 Hospital-based controls without gastric cancer 1
 Cancer-free controls without total description 0.5
 Not described 0
Ascertainment of gastric cancer  
 Histologically or pathologically confirmed 2
 Diagnosis of gastric cancer by patient medical record 1
 Not described 0
Sample size  
 >1000 2
 200-1000 1
 <200 0
Quality control of genotyping methods  
 Clearly described a different genotyping assay to confirm the data 1
 Not described 0
Hardy-Weinberg equilibrium  
 Hardy-Weinberg equilibrium in controls 1
 Hardy-Weinberg disequilibrium in controls 0.5
 No checking for Hardy-Weinberg disequilibrium 0