The utilisation of statistical analysis plan (SAP) has the potential to enhance the reliability, transparency, and impartiality of statistical analysis procedures in the context of clinical studies. These plans are primarily designed for late phase clinical studies, namely phase Ⅱ and phase Ⅲ randomised controlled trials. The extended SAP reporting guidelines for early phase clinical studies, i.e., phase Ⅰ clinical studies and phase Ⅱ non-randomised controlled trials, have been expanded from the original reporting guidelines in six key areas: trial purpose, design, Bayesian statistics, data simulation, sample size, and the application of ICH E9(R1). The expanded reporting guidelines facilitate the standardisation of SAP for early phase clinical trials, enhance the transparency and reproducibility of early phase clinical studies, and thereby improve the quality of early phase clinical studies. This, in turn, plays a pivotal role in later phase clinical studies.
Subpopulation treatment effect pattern plot (STEPP) method is a method for examining the relationship between treatment effects and continuous covariates and is characterized by dividing the study population into multiple overlapping subpopulations to be analyzed based on continuous covariate values. STEPP method has a different purpose than traditional subgroup analyses, and STEPP has a clear advantage in exploring the relationship between treatment effects and continuous covariates. In this study, the concepts, advantages, and subpopulation delineation methods of the STEPP method are introduced, and the specific operation process and result interpretation methods of STEPP method analysis using the STEPP package in R language are presented with examples.