Systematic review and meta-analysis: What are the implications in the clinical practice?

Systematic reviews and meta-analyses, as already reported in the opening article of this section, are the highest level of scientific evidence1 and may strengthen clinically useful evidence.2 That means that, according to evidence-based Dentistry, clinically significant results found in clinical and laboratorial researches will be incorporated in clinical practice, especially in dependence on conclusions drawn from systematic reviews and meta-analyses. For this reason, assessing articles and understanding their findings may be a valuable time saver for every clinician who wishes to introduce new conducts, technologies or treatments into his/her clinical practice in a responsible and scientific manner. Therefore, reading a good systematic review or meta-analysis would prevent clinicians from reading several original research articles (which may be gathered in the systematic review) with a view to reaching a clinical conclusion. However, it is critical for the clinician to read systematic reviews and meta-analyses with a minimum comprehension of their structure and characteristics in order to interpret their findings in a reliable and clinically advantageous manner. Systematic reviews are defined as scientific investigations that attempt to answer focused questions and present pre-planned strategies to include all relevant articles, appraise primary trials and synthesize data, making an effort to reduce bias,3 that means, any tendency usually present in research methodology which may lead to misinterpretation of results. As the name suggests, a systematic review should be performed systematically, with transparency in the report of each step in such a way as to minimize subjectiveness. Meta-analysis may be defined as a statistical synthesis of data4 obtained from original research articles previously gathered by means of a systematic review in which data are comparable. Obviously, since metaanalyses are based on statistical data, they have greater scientific evidence power than a systematic review alone. Systematic reviews and/or meta-analyses should be based on a focused question ideally intended to solve a clinical problem. This question may be described in a PICO/PECO format (Patient/Problem/Population; Intervention/Exposure; Comparison and Outcomes). Therefore, the question should be well constructed in clinical terms, approaching the type of population to be studied. In other words, if the authors will approach a specific group of patients in terms of age, sex or race (P); which type of treatment or intervention/exposure in health is to be investigated (I/E); whether this intervention or exposure should be compared to another kind of treatment or to no intervention at all (control groups) (C); and, finally, the ideal outcomes to be obtained by treatment or exposure (O).