Stepwise covariate modeling

Hi! I am performing stepwise covariate modeling using PsN feature in Pirana. I am getting some covariates which are statistically reducing OFV significantly, however, when I include those covariates in the PK model, the results I am getting are exactly similar to what I am getting in my base model, i.e. there is no difference in individual predictions or pop predictions or any other diagnostic plots. So, does that mean I should move forward WITHOUT including those covariates as they don't seem to be explaining inter-individual variability despite scm telling me that they are statistically significant? Regards, Sumeet K. Singla Ph.D. Candidate Division of Pharmaceutics and Translational Therapeutics College of Pharmacy | University of Iowa Iowa City, Iowa [email protected]<mailto:[email protected]> 518.577.5881