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Evidence-based medicine: the importance of understanding varying levels of evidence

What is evidence-based medicine?

As the continual advancement of the Internet makes access to information only easier by the day, along with it comes an overload of data, and the common difficulty of determining what to believe and what to neglect as false or unfounded. For the medical field, which experiences one of the highest concentrations of inquiries, the process becomes even more complicated and the value of legitimate information even higher.

Evidence-based medicine (EBM), as defined by its main promoter David Sackett, is the conscientious, explicit and judicious use of current best evidence in making clinical decisions about the care of individual patients. EBM uses a system that categorizes research according to its validity, and as a result, allows medical professionals to prescribe the best possible, most proven treatments and tests. This also allows patients to better understand the research process that leads health care decisions.

Evidence by number: rating research by power

Medical professionals are already swamped with the day-to-day obligations of their practice, and free time to scan through all the recent literature in the field is minimal at best. To reduce the time required to devour and assess the strength of every new article published, a system created by the Oxford Center for Evidence-Based Medicine is used that rates research based off of varying levels of evidence (LOE).

Validity, quality of design and applicability to patient care all factor into the levels. Higher numbers signify weak or unproven studies, while lower numbers are assigned to the strongest forms of research that can be relied upon the most. The following is a look a the LOE chart from strongest to weakest with examples of each:

1. Randomized control trials (RCTs): Two groups, identical aside from one receiving an intervention and the other serving as a control, are closely studied


2. • Systematic review: Review of a body of data that uses explicit methods to locate primary studies, and then assesses them using explicit criteria
   
   
   • Meta-analysis: A type of systematic review that uses quantitative methods to assess research from a number of different studies



3. Cohort studies: Groups of people are selected based on their exposure to a particular treatment and followed up for specific outcomes



4. Case-control studies: Subjects (cases) with a condition are matched with controls, and a retrospective analysis is used to determine the differences between the two groups



5. • Case reports/case series: Report based on single patient that can be collected into a short series
   
   
   • Cross-sectional surveys: Survey of a sample of the population of interest



6. Expert opinion: Consensus of experience from expert professionals

Applying Evidence-based Medicine and Levels of Evidence

While critics of EBM exist, accusing it of being old-fashioned or cook book medicine, there's no refuting the proven science of the system. Health care providers that understand the concept of EBM in its entirety, recognize that EBM is far from "cook book medicine". Indeed, EBM not only embraces clinical evidence but also the health care provider's experience and the patient wishes and goals.

Once the validity of research is established using the LOE chart, medical professionals like physical therapists are provided with a clear report of what studies to trust and what treatments are more likely to lead to the most effective results. Having this universal system also makes it easier for patients to comprehend the significance of research and the part it plays in their recovery. Consequently, patients are better prepared to make and understand decisions related to their care as well.