Don’t Trust Your Gut – Part 1
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My dad, a lifelong farmer in central Nebraska, swears by the benefits of a Z-pak (as does his PCP, apparently) for his annual upper respiratory infection. Whenever I get a “cold,” he asks me, “Kyle, aren’t you a doctor? Just prescribe yourself that antibiotic my doctor always gives me. It works every time!” In the past, I’ve responded with a mini-lecture on evidence-based medicine and the benefits of randomization in determining true treatment effects. Now, I respond, “Sure, Dad, and feel better in 5-7 days?” He now gets my joke but continues his annual re-treatment regardless (perhaps in jest?).
We’ve all likely had similar experiences. We’ve taken medications or recommended certain treatments based on some positive experiences. Even more likely, we’ve used or prescribed something because of what we’ve heard about another’s success, whether that be a colleague, a friend, or a key opinion leader. It begs the question: How do we value those experiences and expert opinions?
In the context of our topic of evidence-based medicine, are our experiences and expert opinions a reliable source of evidence? If not, why not? If so, how much should we rely on experience and opinion (whether ours or others) to guide our clinical decision-making? If we rely on experience and opinion, what do we need to be aware of to reduce the risk of poor decision-making in our care for patients?
Evidence-Based Medicine Revisited
Let’s quickly recap what we covered in the last four columns leading up to this point. Our working definition of EBM is the “conscientious, explicit, and judicious use of current best evidence, combined with individual clinical expertise and patient preferences and values, in making decisions about the care of individual patients.”1 The best expression of this in clinical practice is what we’ve described as the Wise Practitioner. The Wise Practitioner is skillfully academic and practical in their approach to assessing evidence with respect to patient care. They see evidence in degrees of certainty, are cautiously aware of their biases, and communicate complexity to their patients to allow for maximum transparency.
But how do Wise Practitioners interpret their own experiences when making better patient decisions? How much, if at all, should they trust their gut?
Although this topic of bias and interpretation of experience is vast and complex, I’ve found it helpful (and reductionist, I admit) always to be aware of three main influences that can deceive us or make us less objective and undermine the reliability of our experience and expertise: the principle of regression to the mean, the inescapable presence of cognitive biases, and the subtle (and not so subtle) influence of industry. In this quarter’s column, we will unpack regression to the mean and leave the rest for future articles.
Regression to the mean
Regression to the mean or toward the mean is a statistical term, but it is also used in medicine to describe the natural history of a condition. Many chronic conditions have acute phases. A good example of this is dry eye disease. Dry eye is a chronic condition with acute phases of flare-ups depending on the environment, underlying etiology, and comorbidities. To understand how regression to the mean applies to our discussion, ask yourself when your dry eye patients usually schedule appointments with you. Is it when their symptoms are managed and minimal or when they are at their worst? Most patients come to see you when their condition is at its worst. If you prescribe X treatment and they always get better, how do you know it was your treatment and not the natural course of the condition? How do you know the patient’s improvement wasn’t just the natural ebb and flow of the condition?
Consider the experience I shared with my dad. The fact that his “cold” improved in 5-7 days might have happened whether he used an antibiotic or not. Like the common cold, many acute and chronic conditions have ebb and flow whether or not we intervene.
So, are warm compresses, topical drops, or intense pulsed light treatments helping our patients’ acute hordeolum? Experience says yes, but how would we know without placebo comparison and randomization? Do topical steroids, lid expression procedures, and other anti-inflammatory drops work for dry eye syndrome? We’ve likely had experiences and heard opinions from experts on this topic. How do we know the difference between our patient just getting better with time (i.e. natural history) despite the treatment?
It is helpful to consider all the treatments we prescribe and whether they could be victims of regression to the mean. How would you know if your prescription or the natural history of their condition correlated most with improvement? The attempt at answering that question leads to the realization of the importance of randomization and placebo and the necessary humility to embrace in making decisions for others.
When we become more aware of a phenomenon like regression to the mean, we become more aware of what we know and what we don’t know. This should instill a more cautious approach to assessing the treatment successes from our own and others’ experiences. Not that we can’t trust personal experience and opinions. However, those experiences and opinions – even expert ones – must be critiqued with the same skepticism that we apply to all other forms of evidence in EBM.
So, just as the Wise Practitioner wisely appraises and applies the randomized controlled trial, they approach experience and opinion with the same objectivity and skepticism.
Have we answered the main question yet? Can we trust our gut? You decide, but you will need to read the upcoming Parts 2 and 3 to be aware of how your cognitive biases and industry influences significantly affect your conclusions.
REFERENCES
1) Sackett DL, Rosenberg WM, Gray JA, Haynes RB, Richardson WS. Evidence based medicine: what it is and what it isn’t. BMJ. 1996; 312:71–72.
Dr. Klute owns and practices at Good Life Eyecare, a multi-location practice in Eastern Nebraska and Western Iowa. He is a fellow of the American Academy of Optometry and is certified by the American Board of Certification in Medical Optometry. He writes and lectures on primary eye care practice management, evidence-based medicine, glaucoma, and dry eye disease.
