I make two to three major mistakes per day. Over time I try to analyze the source of those errors. Errors have developed a bad name, mostly because of To Err is Human, which alleged that 98,000 Americans die annually from inpatient errors, more than MVAs, breast cancer, and AIDS combined. However, without mistakes, there can be no progress.
- Martin A. Samuels, MD
Dr. Samuels framed his discussion through heuristics, or shortcuts in diagnostic reasoning. He posited that, in medicine, such shortcuts are both common and necessary, but that in order to eliminate or decrease the number of mistakes that you might make, you must be aware of the pitfalls in this type of thinking.
In order to do this, Dr. Samuels discussed mistakes he made in five case studies. Each case was a bit too in-depth to try to capture all of the information presented, but understanding the basic lesson behind each is more the point.
Beware the framing effect
Presented with the case of a 49 year old woman who developed a rapidly progressive weakness while vacationing in Mexico, Dr. Samuels indicates that he got hung up on the fact that she got sick in Mexico.
It turned out that he didn’t pay enough attention to the patient’s history which should have tipped him off to the fact that she did not have a primary neurological disease. “Not everyone in Mexico has a regional disease.”
Beware of the availability heuristicAfter correctly diagnosing a 42 year old African American teacher with autoimmune gastritis, he incorrectly diagnosed a 74 year old man presenting with the same symptoms with the same disorder.
However you term it—last case bias, anchoring—the problem is one of stubbornness.
“Once you make a correct diagnosis, it seems that all of a sudden everyone has it,” Dr. Samuels explains. “But the likelihood of seeing a case of something is not influenced by having seen a similar case recently.”
Beware of blind obedience
In the case of a 50 year old, left handed woman complaining of headache, neck stiffness and nausea for 2-3 months, Dr. Samuels suspected that she had herpes simplex encephalitis; however, her HSV PCR came back negative.
A 46 year old man complains of gradually worsening generalized, non-descript headache, which is worse on standing and improves when lying down. During his service in the Army, he had several head and neck injuries, but never lost consciousness. After reviewing some head scans, Dr. Samuels made his diagnosis.
In the first case, Dr. Samuels was right. A second HSV PCR came back positive. In the second case, blood tests revealed that the former soldier had contracted syphilis during his service. Dr. Samuels uses these two cases to caution against blind obedience to tests. In the first case, he was overly-discouraged by the negative laboratory test; in the second, he relied too much on the imaging appearance.
Beware of hubris
A 61 year old man complains of headaches in the past, but over three months he developed a new type of right sided pain. He had a right sided vestibular schwannoma successfully resected five years ago with only limited right side weakness not related to surgery.
Dr. Samuels initially diagnosed him with chronic paroxysmal hemicrania, but when the patient called a month later to report a recurrence of pain with black eye, Dr. Samuels triumphantly changed his diagnosis, telling everyone he could. “All were kissing my feet,” he said.
Unfortunately, a neuroradiologist reviewed the patient’s CT and spotted a nasopharyngeal cancer that was missed. He was wrong too. A rheumatologist finally made the correct diagnosis: Wegeners granulomatosis.
Experts are called experts for a reason
Not all errors are due to heuristic misuse. Dr. Samuels has shown the brain scan of a particular patient to numerous neurologists and every one of them has recognized that something is wrong with the patient’s bone marrow; no primary care physicians have.
“Who says we don’t need experts?” asks Dr. Samuels. “Don’t undervalue the special expertise that we can get from real experts.”