I can’t stress enough the importance of having a solid and to-the-point research protocol before you start a new research project. Whether your study is going to be a multi-center randomized controlled trial or even a small prospective or retrospective cohort study, a research protocol makes your life easier and your study more valid. Here is why:

Internal validity
All research is incremental and all the improvements we aim to achieve by doing clinical research are aimed at getting a somewhat better understanding of the underlying truth. Although it sounds appealing, it is quite unlikely that we actually experience “break-trough science” anytime in our career. This means that the research we do should be as accurate and valid as possible, so that we are able to detect small and large effects alike.

The way modern-day statistics are set up makes the tests we do reliable, but it also limits us to using a strict framework. This framework includes defining the exposure(s) of interest, primary endpoint and secondary outcomes, setting a null hypothesis, and state which statistical parameters and test you are going to use for the analysis, before you actually start the study.

If you record all these parameters in your study protocol, it will be more likely that you adhere to them throughout the rest of the study. This will eventually improve your internal validity, which reflects the accuracy and validity of your conclusions.

External validity
Clinical research is typically performed in a sub set of the general population. We control the environment to improve feasibility and internal validity of our research. Although the internal validity is most important, eventually you would like to apply the results of your study to a larger population (generalize). The degree to which this is possible depends heavily on the external validity of your study.

If you clearly define the inclusion and exclusion criteria in your study protocol, this will enable you to think about whether your study is going to be generalizable before you start. It will also impact to what extent readers are going to be able to apply your conclusions to their individual setting.

Bottom line
Most of the problems that occur by not thinking about these issues ahead are very difficult (if not impossible) to fix after your study ends. You save a lot of trouble if you create a clear study protocol and discuss it with your clinical and scientific co-workers.

A good study protocol will result in higher internal and external validity and thereby improve the odds of publication in a high-impact journal!