It may not be possible to tell what criteria the author used in selecting the studies to be included or excluded. Guidelines are developed using widely varying standards. Cost may be considered as well as health outcomes. Research Articles Research articles are published results of research studies. Occasionally you can find structured commentaries on research articles.
Research articles vary in the level of detail given about the study.
You may need to do your own evaluation. Meta-Analyses Systematic reviews use explicit methods to identify, select, and critically evaluate relevant research. Meta-analyses are systematic reviews that combine the results of several studies using quantitative statistics. Before using information as the basis for patient care, you must assess its scientific and clinical merit. The Users Guides to Evidence-Based Medicine provide useful questions to guide your evaluation.