The hierarchy of evidence: Levels and grades of recommendation

E vidence-based medicine requires the integration of evidence, that is, some studies are better suited than others, clinical judgment, recommendations from the best to answer a question of therapy, for example, and may available evidence and the patient’s values. The more accurately represent the “truth”. The ability of a study “best available evidence” is used quite frequently and in to do this rests on two main contributing factors, the study order to fully understand this one needs to have a clear design and the study quality. In this context we will focus knowledge of the hierarchy of evidence and how the for the most part on those studies addressing therapy as integration of this evidence can be used to formulate a this is generally the most common study in the orthopedic grade of recommendation. It is necessary to place the surgical literature. available literature into a hierarchy as this allows for a clearer communication when discussing studies, both in Available therapeutic literature can be broadly categorized day-to-day activities such as teaching rounds or discussions as those studies of an observational nature and those with colleagues, but especially when conducting a studies that have a randomized experimental design. The systematic review so as to establish a recommendation for reason that studies are placed into a hierarchy is that those This necessarily requires an understanding of at the top are considered the “best evidence”. In the case both study design and quality as well as other aspects which of therapeutic trials this is the randomized controlled trial can make placing the study within the hierarchy difficult. (RCT) and meta-analyses of RCTs. RCTs have within them, Another confounder is that there are a number of systems by the nature of randomization, an ability to help control that can be used to place a study into a hierarchy and bias. Bias (of which there are many types) can confound depending on the system a study can be placed at a the outcome of a study such that the study may over or different “level”. However, in general the different systems underestimate what the true treatment effect is. rate high quality evidence as “1” or “high” and low quality Randomization is able to achieve this by not only evidence as “4 or 5” or “low”. Recently, some orthopedic controlling for known prognostic variables but also and journals have adopted the reporting of levels of evidence more importantly controlling for the unknown prognostic with the individual studies and in many cases the grading variables within a sample population. system has been adopted from the Oxford centre for act of randomization should be able to create an equal evidence-based medicine system. Rather than refer to any distribution of prognostic variables (both known and particular system we will speak in general terms of those unknown) within both the control and treatment groups studies deemed to be high-level evidence and relate this within a study. This bias-controlling measure helps attain to those of lesser quality. a more accurate estimation of the truth. Those studies of a more observational nature have within their designs areas practice.