Genetic susceptibility and environmental factors of esophageal cancer in Xi’an

Table 2 Synergic interactions of tobacco smoking and GSTM1 deletion genotype

Tobacco smoking	GSTM1 deletion	Case	Control	OR	OR95%CI	χ2	P
No	No	24	37	1.00
No	Yes	33	26	2.96	0.89-4.33	3.28	0.07
Yes	No	29	20	2.24	0.97-5.19	4.24	0.04
Yes	Yes	41	18	3.51	1.55-8.05	10.89	0.001

SIA = 3.51 / (2.24 + 1.96 - 1.00) = 1.10. SIA: Synergic index of addition.