Interaction estimation

[yinglittxs]

Dear professor: I would like to ask you a question regarding interaction in multi-state model. The interaction effect of the multiplication of the two factors can be evaluated by adding the product term to the model. If the additive interaction effect is to be tested, can the RERI = HRa+b + -HRa+b - -HRa-b + +1 be used for calculation based on the HR estimated by MSM (i.e. method estimating RERI for logistic and cox)?

[chjackson]

I do not have any experience with using this metric, but if it is applicable to Cox models, then it would also be applicable to msm models, since the effects can be expressed as hazard ratios in both.

[yinglittxs]

Thank you very much