ABSTRACT
A single, even epidemiologically impeccable study, does not always answer all of the important questions in a particular area of medical work. Does jogging do more harm than good? Is diethylstilbestrol a predominant cause of clear cell vaginal carcinoma? Do beta-blockers prevent death after myocardial infarction? Is the BCG vaccine equally effective around the world? Chapter 8 stresses consistency of findings as one of the criteria of causality. Systematic reviews of evidence are meant to uncover whether findings about a health problem are consistent across the body of available original studies and valid information in the literature. Readers of medical journals quickly realize how complicated and diversified information becomes. Original studies multiply fast and exponentially, especially in such crucial fields as cardiovascular disease and cancer, among others. These studies, as comprehensive as they may be, do not give homogeneous results across often enormous bodies of accumulated knowledge on a single subject. These studies are followed by ‘review articles,’ ‘position papers,’ ‘consensus on …’ with recommendations to practitioners as to what and how to diagnose, what treatment to choose, etc. To accept or refute such recommendations and translate them into office decisions or further research is crucial for patient well-being, for institutional budgets and for good medicine and/or research. By analyzing and summarizing bodies of evidence, clinicians seek new and better premises and conclusions for logical arguments, supported by the best available evidence.
This chapter is about such a summarizing of evidence across its principal components, namely meta-analysis in medicine (a mostly quantitative methodology) and systematic reviews of evidence (a mostly qualitative approach).
