Parallelism is the prerequisite assumption that the test product behaves like a dilution or concentration of the reference product. It is the basis for defining the relative potency of a test product to the reference standard. Once parallelism between the test and reference curves is established, the relative potency will be constant at any effective response levels. This paper presents a review of most proposals for parallelism testing via significance, equivalence, and similarity testing approaches. The pros and cons of each proposal with equivalence margin determination are discussed. Recent approaches for testing parallelism are introduced in the paper.
Wang et al. (Sun,) studied this question.