Table 1.

Score categories for an interaction between an environmental agent and a genetic variant based on the strength of evidence for a main effect of each of them (1 = strong, 2 = moderate, 3 = weak)

	Evidence for environmental main effect
Evidence for genetic main effect	A (strong)	B (moderate)	C (weak)	D (lack); E (evidence against)
Strong	1	2	2	3
Moderate	2	2	3	3
Weak	2	3	3	3
Lack; evidence against	3	3	3	3

See criteria for defining strong, moderate and weak for environmental exposures in Table 2 and genetic effects in Table 3.