A document that lays out the research plan before conducting the study. The protocol is designed to describe the study methods and procedures, potentially allowing for its replication. The protocol should clearly detail the following information: the reason for conducting the study, the definition of the target population (the eligibility criteria), the number of participants to be included, the description of the interventions being studied, the schedule of tests and diagnostic procedures, drugs and their dosages, the length of the study and the participants’ data. Sometimes, the protocol is prepared by the researchers with the collaboration of patients or their representatives. Each clinical study protocol has to be registered in ad hoc institutional databases (USA www.clinicaltrials.gov , EU www.clinicaltrialsregister.eu/ ).
