ETAPvalues

Dear Nonmem users, My question is about ETAPval. I am modelling a parent-metabolite data using the 2-stage approach. After modelling the parent drug alone, parameter estimates (for the parent) were fixed in the metabolite model and metabolite parameters were estimated. All ETAPvalules for metabolite parameters were acceptable > 0.2 and all metabolite model parameters were estimated precisely; however, some of the ETAPvalues of parent drug parameters became < 0.05 while they were acceptable when the parent drug was modelled alone. Should ETAPvalues for parent parameters stay above the acceptable limit even if the parameters are fixed or we care only about the ETAPvals for estimated parameters only? N.B. Simultaneous modelling of the parent-metabolite wasn't possible. Thank you, Ahmad Abuhelwa Email: [email protected]<mailto:[email protected]> Mobile: +61 413118743