A study in the January 10, 2011 issue of the Archives of Internal Medicine reports that more than 50% of the 4,218 recommendations in guidelines issued by the Infectious Diseases Society of America were based on level III evidence -- the lowest possible category.
    Level lll evidence is the opinions of respected authorities based on clinical experience, descriptive studies, or reports of expert committees.
    Don Heun Lee, MD, and Ole Vielemeyer, MD, of Drexel University in Philadelphia, say that doctors sometimes assume that following practice guidelines means they are practicing quality, evidence based medicine. However, they say, the quality of the supporting literature varies greatly.
    Only 14% of the recommendations were linked to the highest level of evidence with 55% supported only by expert opinion.
    In an accompanying editorial, John Powers, MD, of Scientific Applications International Corporation in Bethesda, Md., said the findings "reinforce that absolute certainty in science or medicine is an illusion."
    He goes on to say the message is to "be wary of falling into the trap of 'cookbook medicine,'" adding that "guidelines will never replace critical thinking in patient care."
    "Although the evidence and recommendations in guidelines may change across time," he wrote, "providers will always have a need to know how to think about clinical problems, not just what to think."