Abstract
Background: Randomized clinical trials have been considered as the gold standard for evaluating the effectiveness and safety of medical interventions; however, there are major barriers to their design, conduct, analysis, and reporting. They are multidisciplinary and involve different steps and face a variety of challenges that may vary from one country to another. The aim of this study was to provide a comprehensive presentation of the challenges of clinical trial studies in different steps including design, conducting, analysis, and reporting. Methods: In this study, all original articles conducted during 1991-2017 that reviewed the barriers to clinical trial studies at one of the steps of design, conducing, analysis, and reporting of the results in Medline (through PubMed), Embase, Web of Sciences, Scopus, and Google Scholar were considered. The searched keywords were as follow: challenges, barriers, and randomized clinical trial. Results: The following barriers in different steps of randomized clinical trials were identified: general barriers include insufficient knowledge and understanding of clinical research and research methodology, barriers to ethical and regulatory systems, and lack of funding. The investigator-initiated trials may face similar problems to those of sponsor-initiated trials, such as handling regulatory systems, administrative and financial issues, multiple languages, and different patient compensation approaches. The challenge related to design was poor planning. Other challenges were lack of manpower and financial resources, inappropriate statistical methods for analysis (analysis challenges), and challenges related to reporting which include selective reporting. Conclusion: Based on the results of this systematic review, the most important challenges were barriers related to handling ethical and regulatory systems, patient recruitment, and lack of budget and skilled staff for conducting clinical trials. Training to improve the quality of randomized clinical trial studies in different steps and levels was the most important recommendation in these studies.