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Table 1 Scale for quality assessment

From: XPC Lys939Gln polymorphism contributes to colorectal cancer susceptibility: evidence from 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 colorectal cancer 1
Cancer-free controls without total description 0.5
Not described 0
Ascertainment of colorectal cancer  
Histological or pathological confirmation 2
Diagnosis of colorectal 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