Confirmation bias in both physicians and patients

We are all guilty of confirmation bias from time to time.

Confirmation is something that resident physicians in particular are guilty of more so than experienced, qualified physicians.   Resident physcians and attending physicians alike may quickly form a diagnosis in their mind during a brief discussion with a patient.  Now they will try to convince themselves (sub-consciously) that the other complaints and physical exam fit that diagnosis.   They force the rest of the interaction in a certain direction.  Surprisingly, when a cross sectional study such as an MRI does not reveal the diagnosis they were suspecting, the usual response is that the MRI “missed it.”  And the confirmation bias persists.

I have seen many second opinions when the patient either had surgery or plans surgery for a presumed diagnosis, not yet confirmed with imaging studies.  After taking 5 to 10 minutes to listen to the patient, the real diagnosis usually reveals itself.   Now, I’m not claiming to be Dr. House (who is guilty of confirmation bias too), but I certainly give the patient enough time to talk until a solid list of differential diagnoses have formed in my mind.   And we don’t stop talking until that occurs.  If the light bulb doesn’t illuminate, I simply say “I don’t know” and “let’s go to the computer and look this up.”

This is a very important concept for residents to grasp early on in their training.  Not all snapping in the knee is a meniscus tear, not all shoulder pain is a rotator cuff tear and not all back pain is a pinched nerve.  Listen to your patient, ask the right questions and the correct diagnosis will usually reveal itself.

Patients are also guilty of confirmation bias.  When many patients are online looking for information, they are usually (certainly not always) starting with a presumed diagnosis given by a physician, friend, or a Googled page.  Now they search deeper and deeper into that diagnosis, even if the hints are there that this may not be the correct diagnosis.  It is not very hard to force a soft square object into a hexagon shaped cup.

One of the roles of experienced physicians and diagnosticians is to educate residents, colleagues at the water cooler and, of course, patients.  Patients are online and searching.  If they start their search with a reasonable foundation and instructions on how to minimize confirmation bias, a more educational and more productive search will ensue.

Howard Luks is an orthopedic surgeon who blogs at his self-titled site, Howard J. Luks, MD.

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  • Anonymous

    Thanks, Dr. Luks, for this comprehensive overview of confirmation bias.  I’d suggest, however, that it isn’t just those young residents who are overeager to jump on a diagnosis “more so than experienced, qualified physicians”, as you say.  (Consider Dr. Jerome Groopman‘s excellent book, ‘How Doctors Think’, for example, for illustrations of what he calls “The 18-Second Rule” – that’s how long a doctor will sit quietly before interrupting a patient with a diagnosis).

    I was sent home from the E.R. with an acid reflux misdiagnosis (in mid-heart attack!) by one of those “experienced, qualified” middle-aged, grey-haired, starchy-white coat-wearing physicians despite presenting with textbook symptoms like chest pain, nausea, sweating and pain radiating down my left arm.  “You’re in the right demographic for GERD….” was how he arrived at his misdiagnosis. More on this at: “Seven Ways To Misdiagnose a Heart Attack” – http://myheartsisters.org/2011/05/09/misdiagnosed-heart-attack/  which includes the concept of confirmation bias and six other forms of diagnostic bias that can blind physicians (and patients!) to reality.

    Your reminder to physicians and residents is timely and important. Thank you for this!

  • http://www.facebook.com/people/Jackie-Swenson/100000046998781 Jackie Swenson

    The diagnosis of my life-long brain tumor was delayed for at least a couple of years after I began to experience symptoms.  My family doctor, whom I was introduced to by my supervisor at my new job in a new town just two and half years prior, believed that I was suffering from ‘tension headaches’ and was over-stressed at work.  He ‘knew’ it bacaus my supervisor, his long-time patient and friend, was suffering from the pressure of our new Director.  The Director was giving the 63-year-old 2nd-in-command lots of ‘physically-demanding’ tasks in order to force her to retire.

    What the doctor did not know was that I was actually ‘taken under the wings’ by the new Director.  My headaches were caused by a huge brain tumor lodged in the center of my brain.  I went panicking when I realized he was not looking at the right direction – he dismissed any ‘physical cause’ of my headaches and ‘threatened’ to give me a referral to a psychiatrist!  So I switched to another family physician within the same network.  Also young and well-known in the local area, this doctor listened to me for just a couple of minutes and declared: “Oh– Allergy!  You need to move!” aftrer I had mentioned my symptoms were a lot worse during the allergy season.  Out of desperation, I asked him where  I should moved to.  And he answered with assurance: “Nevada or Arizona.”

    It took a retired pathologist, who’s a volunteer at my worksite, to nudge me in the right direction.  She told me my dizzy spell was a ‘serious’ condition that required medical attention.  She even chewed out the receptionist over the phone for me when I was ‘advised’ to ‘wait till the allergy season is over’.  Eventually I had had a craniotomy that took 23 hours to resect a 4x5x6.5 cm Central Neurocytoma…

    Similar situation happend when I was requesting for a prophylactic procedure because of a new cancer incident in my family.  My current family doctor, whom we’ve known for ten years, was reluctant because he had seen me ‘under stress’ a couple of times.  He thought my personal cancer experience had turned me into a hypochondriac.  He wanted med to get a second opinion.  So I turned to my oncologist and received an ‘OK’ through the oncology nurse.

    My genetic testing result less than a year prior revealed a ‘variant of uncertain significance’.  But after the third family cancer case, this time a sibling, I was certain that I needed to be pro-active on my own behalf.  Doctors can’t know every details of our family/personal history.  They need our help.

  • http://twitter.com/litigationtech Ted Brooks

    Dr. Luks -

    Thank you for sharing this information. I was directed to this article after posting a similar position regarding the litigation process: http://trial-technology.blogspot.com/2011/09/cant-see-forest-for-trees.html

    The common thread is the importance of getting another set of eyes to look at the situation, and that they are unbiased, and unfamiliar with the background and details of the case.

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