Bioequivalence and Bioavailability Forum

Dear Elmaestro !

I am definitely not proposing R squared to assess dose-proportionality. you can assess the relation between dose and AUC/Cmax using the power-law model. the power-law model allows you to estimate a “proportionality parameter” along with a confidence interval (CI). based on these results you can assess dose-proportionality (testing for difference / testing for equivalence). calculation details can be found in the mentioned paper of Hummel et al. (2008).

the width of the CI for the proportionality parameter clearly depend on the sample size used as with every statistical method. however, this CI gives you an estimate for the size of a potential disproportional behavior which can be used to assess the effect in terms of clinical relevance AND in term of statistical significance.

note that Hummel et al (2008) suggest a rather wide acceptance range to accept dose-proportionality which may be motivated for the reasons you pointed out.

best regards

Martin