Table 4.

Measures from the departure-from-additivity model for the joint effect of CFH rs1061170 and HTRA1 rs3793917 with nAMD.

Measures	Estimate	Lower 95% CI	Upper 95% CI
The synergy index (S)A	2.63	1.09	6.38
AP (%)B	55.70%	21.40%	89.90%
RERIC	5.44	−1.71	12.59

^AThe synergy index (S) was estimated by the formula (RR₁₁ − 1)/((RR₁₀ − 1) + (RR₀₁ − 1)).

^BAP, the attributable proportion due to interaction, was calculated using RERI/RR₁₁.

^CThe relative excess risk due to interaction (RERI) was calculated by RR₁₁ − RR₁₀ − RR₀₁ + 1.

RR₁₁, RR₁₀, and RR₀₁ were relative risk exposed to both two factors, only the first factor, and only the second factor, respectively.