# Table 3

Calculating measures of biological interaction between genotypes and environmental exposures

Dichotomous risk factors

RR

95% CI

RERI

AP

S

Risk 1a(Genotypes)

Risk 2

lower

upper

GSTT1*0/*0

alcohol

2.158

1.175

3.965

-0.322

-0.149

0.783

GSTT1*0/*0

smoking

1.771

0.958

3.274

-1.559

-0.880

0.331

GSTT1*0/*0

wood/charcoal

2.738

1.443

5.198

0.213

0.078

1.140

GSTM1*0/*0

alcohol

0.399

0.165

0.760

0.058

0.145

0.912

GSTM1*0/*0

wood/charcoal

1.075

0.508

2.276

-1.641

-1.527

0.044

GSTM1*0/*0

smoking

0.364

0.190

0.699

-0.148

-0.407

1.304

GSTP1 313 A/G +G/G

alcohol

0.922

0.488

1.743

0.597

0.647

0.115

GSTP1 313A/G +G/G

smoking

0.779

0.390

1.553

0.113

0.145

0.663

GSTP1 313A/G +G/G

wood/charcoal

1.738

0.978

3.087

0.185

0.107

1.335

GSTP1 341C/T+T/T

alcohol

6.321

3.054

13.09

-0.514

-0.081

0.912

GSTP1 341C/T+T/T

smoking

4.284

2.158

8.507

1.032

0.241

1.458

GSTP1 341C/T+T/T

wood/charcoal

29.87

8.968

99.49

27.38

0.917

19.40

aThe references for the interaction exposures were; GSTM1*1 + non-exposure, GSTT1*1 + non-exposure, GSTP1 313 A/A + non-exposure, GSTP1 341 C/C + non-exposure. Where non exposure refers to any of the following; non-smoker, non-alcohol consumer, and not exposed to use of wood/charcoal. The interaction model used could only factor in two dichotomous risk factors. Thus the following genotype combinations were used; GSTM1 (GSTM1*1/*1 vs. GSTM1*0/*0); GSTT1 (GSTT1*1/*1 vs. GSTT1*0/*0); GSTP105 (A/A vs. A/G+GG); GSTTP114 (C/C vs. C/T+T/T). For each interaction, four disjoint categories were created. For example, in the case of smoking and GSTP114 (non-smoker and C/C, non-smoker and C/T+TT, smoker and C/C, smoker and C/T+T/T). RR= relative risk; RERI = the relative excess risk due to interaction; AP = the attributable risk due to interaction; S = the synergy index.

Li et al. BMC Genetics 2010 11:47   doi:10.1186/1471-2156-11-47