Association between COX-2 -1195G>A polymorphism and gastrointestinal cancer risk: A meta-analysis

Table 1 Quality evaluation scale of the included literature

Criterion	Score
Representativeness of cases
Selected from population or cancer registry	3
Selected from hospital	2
Selected from pathology archives, but without description	1
Not described	0
Source of controls
Population-based	3
Blood donors or volunteers	2
Hospital-based (cancer-free patients)	1
Not described	0
Case-control match
Matched by age and gender	3
Not matched by age and gender	0
Specimens used for determining genotypes
White blood cells or normal tissues	3
Tumor tissues or exfoliated cells of tissue	0
Hardy-Weinberg equilibrium (HWE)
Hardy-Weinberg equilibrium in control subjects	3
Hardy-Weinberg disequilibrium in control subjects	0
Total sample size
> 1000	3
> 500 and < 1000	2
> 200 and < 500	1
< 200	0