Table 3

Meta-analysis of case–control studies for GSTM1, GSTT1, and head and neck cancer

GSTM1GSTT1
No. of studiesORa for null genotype (95% CI)Test for heterogeneityEgger’s testNo. of studiesORa for null genotype (95% CI)Test for heterogeneityEgger’s test
Overall301.30 (1.12–1.50)0.000.02211.17 (0.98–1.40)0.010.97
 Excluding studies26b1.23 (1.06–1.42)0.000.99
Cancer site
 Oral10c1.45 (1.05–2.00)0.000.317d1.15 (0.82–1.63)0.100.44
 Larynx9e1.10 (0.86–1.41)0.020.657f1.00 (0.74–1.36)0.090.77
Smoking status
 Never smokers4g0.98 (0.58–1.65)0.850.78
 Ever smokersh8i1.37 (0.97–1.94)0.000.595j1.24 (0.92–1.66)0.240.90
Region
 Asia91.58 (1.16–2.14)0.000.2961.31 (0.88–1.96)0.040.99
 North America61.24 (0.98–1.57)0.170.7661.59 (1.12–2.26)0.170.34
 Europe111.02 (0.90–1.15)0.570.9190.96 (0.81–1.14)0.630.43
Year of publication
 1995–1999141.22 (1.03–1.43)0.040.4591.14 (0.87–1.48)0.040.50
 2000–2003121.24 (0.96–1.59)0.000.65121.20 (0.93–1.55)0.020.69
No. of cases and controls
 <100 cases or <100 controls91.42 (1.16–1.74)0.450.6991.26 (0.86–1.85)0.040.02
 ≥100 cases & 100≥controls171.16 (0.97–1.39)0.000.16121.14 (0.93–1.39)0.020.47
Control source
 Hospital-healthy or population161.27 (1.02–1.59)0.000.02121.03 (0.85–1.25)0.170.77
 Hospital101.17 (1.02–1.34)0.660.9691.41 (1.04–1.93)0.030.64
Matching
 Individual matching71.38 (0.92–2.08)0.000.1671.50 (1.01–2.22)0.030.50
 Frequency matching51.07 (0.89–1.27)0.690.9341.30 (0.98–1.71)0.910.83
 No matching141.21 (1.02–1.43)0.020.15100.97 (0.79–1.18)0.220.70