Can I use models other than those described in chapter 5.3 of the European Pharmacopoeia?

Answer:

Chapter 5.3 of the European Pharmacopoeia is not mandatory. It is intended to be a guide for those whose primary training and responsibilities are not in statistics, but who have responsibility for analysis or interpretation of the results of these assays, often without the help of a statistician. Alternative methods may be used, provided that they are equally reliable. The core engine of CombiStats implements the unifying theory of Generalised Linear Models, which cover all models described in chapter 5.3 plus many more.