If this were not available, clinicians would use other types of studies or expert-based opinions. Advantages of randomized clinical trials include reduction in bias since the groups are randomly assigned to various treatments or placebo. Neither patient nor the investigator knows who received which therapy. Utilizing longitudinal studies, which follow large groups, can provide information about the long-term effects of treatment or the natural history of a disease. Cross-sectional studies look at patients treated with different modes of therapy at a single point of time.
Case reports provide information about new clinical techniques, often with detailed methods.
They aren't designed to provide an unbiased estimate of the efficacy of the treatment. Animal and laboratory studies provide important information that can be used to improve the design of human clinical trials. Meta-analysis of the literature can be used also as well as anecdotal clinical observations but only as a last resort if other information isn't available. Answering some of these important questions will help to develop the critical skills necessary to evaluate the research literature and better determine if a direct application to our clinical practice may be made. If some of these questions don't provide the appropriate answers, there may be crucial faults to the study, which may render it inadequate for clinical application.