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Evidence-based Medicine: Defining Evidence

The overall goals of evidence-based medicine (EBM) are to provide physicians and medical
personnel with the best information available in the field so that the clinical practices of these
professionals provide patients with the best possible care. 



The Philosophy of Evidence-based Medicine

Science and Medicine: Objectivity vs. Subjectivity

Medical Rhetoric as a Social and Communicational Construct

The Social and Rhetorical Implications of Medical Discourse

The Social and Rhetorical Implications of Defining Evidence



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Science and Medicine: Objectivity vs. Subjectivity

In the Western world, we are brought up to think of science as a means of discovering the truth about the world we live in.  This truth consists of facts and questions that have answers that are right or wrong (i.e., true or untrue) and, most often, only one answer is the right one.  This idea of absolute truth leaves little or no room for interpretation—something is one way or it isn’t—meaning that all observations must be purely objective since anything that invites interpretation cannot be certain, and therefore, must not be truth.  While the concept of objective observation is key to the scientific method, which is in turn the foundation for science as we know it today, there are arguments that wholly objective observation may not even be possible.  Barry Brummett argues, “The very nature of observation, the approach towards the observed by the observer, is a linking of the two.  Real detachment would mean no observation at all.  Observation is participation...” (157).  Brummet is saying that in order to observe, the observer enters a situation, therefore altering the situation merely by being present.  While this idea is very disturbing to many scientists since it suggests that uncorrupted reality will then never be known to humans, it is not a new concept for science: quantum mechanics has faced the same problem since the conception of the study.  As far as anyone knows at this time, it is impossible to study quantum physics without interfering with the natural state of the material.  On a simpler conceptual level, when a wild animal senses that it is being observed, its behavior changes to reflect the state of being watched and in potential danger. 

Medicine, being a child of the sciences, valiantly struggles to adhere to this ideal of right or wrong answers although all too often humanity gets in the way.  The need to balance this idea with the realities of working with actual people is very apparent throughout the text by Sackett et al.  This conflict is illustrated right away in the introduction to the text. One of the steps prescribed for practicing EBM is “critically appraising that evidence for its validity (closeness to the truth)” (Sackett et al. 4).  Even within this sentence we see the need for a single truth—“the truth”—even while the search for that truth or the likeness to it is subjective—“critically appraising,” a subjective process based on personal judgment.  

EBM’s next internal conflict comes in the practicing of EBM: incorporating patient testimony into a clinical analysis.  Needless to say, a patient’s personal testimony is highly subjective since the only means of measurement and analysis are the patient’s own experiences thus far (e.g., where in the body is the pain located? or how intense is the pain? [Sackett et al. 26]).  This information is crucial to medical diagnosis since there is no other readily available means of determining this information in a more controlled, objective manner, and so despite the fact that this information is highly subjective, it cannot be ignored.  The EBM text that is being examined labels this information as being “qualitative research” and implies that this information from personal experience is inferior to “‘objective’ effects of quantitative research” (Sackett et al. 21, 22).  The text smoothly dismisses this issue as not being in their area of expertise and yet states “we regard the integration of qualitative research to be one of the major current challenges in EBM” (Sackett et al. 21).  Therefore, the question becomes is this qualitative research/patient testimony evidence or some other sort of information?  The EBM training text seems to suggest that it is something other than evidence by their definition, since there is not a means of determining this information’s “closeness to the truth.” 

In practice, medical personnel often try to compensate for this human subjectivity by recounting patients’ testimonies in medical jargon and in the passive voice, which often gives the illusion of objectivity.  This tendency to objectify people and their subjective experiences is illustrated in a study by Kathleen Welch of the University of Missouri-Kansas City.  This study took traditional medical students and required them to take a three-hour literature class that focused on literary connections to medicine along with students from other disciplines.  The medical students enrolled in this course had an overwhelming tendency to focus on the disease or medical condition involved in the story, which is not terribly surprising; however, these students also used language that objectified the people in the story, ignoring the personal experiences of the patients and any factors that were not related to medical diagnosis or the specific plotline (Welch 313–317).  These students are a good representation of the medical field’s focus on the objective to the point of ignoring or altering the subjective to fit preconceptions of what evidence should be. 

This trend is found throughout the medical field and the EBM text examined here and it has not gone unnoticed by practitioners.  An editorial by Trisha Greenhalgh in the British Journal of Medicine provides a good argument temporizing the sweeping claims and generalizations that are often found in pro-evidence-based medicine texts.  She highlights the issues of patients with a complex medical history, which have many aspects and considerations, and the possible treatment approaches: “Failure to recognize the legitimacy of these variations in approach has created a somewhat spurious divide between those who seek to establish general practice on an equal ‘scientific’ footing to that of the secondary care sector and those who emphasize the value of the intuitive, narrative, and interpretive aspects of the consultation” (Greenhalgh 958).  This still does not categorize this subjective information as evidence, but it at least acknowledges the value of it.

Written by Amanda Fullan, University of Wisconsin, Eau Claire
Last Updated December 15, 2001