I have data for a single arm pre-post study for which one of the outcomes of interest only has measures at the follow-up visit (this is part of the study design). Several potential predictors have measures at baseline and follow-up.

I am wanting to know in the simple case of a univariate regression with one of these predictors, what are the potential implications of using both (baseline and follow up) measures vs the change score vs follow-up measures only? (remember this is for the independent, not dependent variable case).

I have done several analyses already and included both measures of each predictor in these regression models. I largely based this decision on comments in this stack exchange thread (for which Frank commented also):

It’s now been suggested to me now that this is not an optimal approach and I should consider using just the follow-up measures.

I’m trying to work out if one approach is better. Interested in people’s thoughts - thank you.