Table 1.

Scale for quality assessment

Criteria	Score
Source of cases
Selected from population or cancer registry Selected from hospital Selected from pathological archives, but without a description Not described	3 2 1 0
Source of controls
Population-based Blood donors or volunteers Hospital-based (cancer-free patients) Not described	3 2 1 0
Specimens obtained from patients to determine genotypes
White blood cells or normal tissues Tumor tissues or exfoliated cells of tissue	3 0
Hardy-Weinberg equilibrium in controls
Hardy-Weinberg equilibrium Hardy-Weinberg disequilibrium	3 0
Total sample size
≥ 1000 ≥ 500 but < 1000 ≥ 200 but < 500 > 0 but < 200	3 2 1 0