We all trust in doctors to diagnose whatever is wrong with us when we feel ill. After years of training, perhaps some form of specialisation, we have confidence that a doctor will be able to pinpoint the cause of the ailment and prescribe a way to fix it. Understandably, as there might be a miscommunication between what the patient describes and how the medical professional understands, there might be a misdiagnosis, the question is, how often does it occur, and can the reasons be isolated and addressed?
Research in the U.S. has shown that medical misdiagnosis is the third largest killer in the cause of death. The team from Johns Hopkins, publishing in British Medical Journal, argued that the CDC’s (Centre for Disease Control) way of collecting health statistics fails to classify medical errors separately on the death certificate. Further, the problems created by inaccurate medical diagnoses far exceed those due to drug prescription errors. The numbers are substantial, about one-third of malpractice cases result in death or permanent disability and come from either a misdiagnosis or a delayed diagnosis. Approximately 12 million Americans suffer a diagnostic error each year in a primary care setting and 40,000 to 80,000 of them die.
Part of the problem is doctors concentrating in certain disciplines. Many of the errors occur because specialists tend to diagnose according to their specialties. For example, consider the following hypothetical diagnosis: a gastroenterologist diagnosed patient X with abdominal pain as viral gastroenteritis, a cardiologist sent the same person to a coronary care unit, and a nephrologist concluded that the pain was the result of kidney stones. The actual cause was eventually found to be a ruptured appendix. In this instance, it was not fatal for the patient, but it could have been.
About one-third of medical malpractice cases result in death or permanent disability and come from either a misdiagnosis or a delayed diagnosis.
Research by Ahmad Hashem and co-authors, published in the Journal of Biomedical Informatics examined “Medical errors as a result of specialisation”, and explicitly tested the hypothesis that physicians have a bias towards diagnosing inconclusive cases as being within their domain of expertise. They recruited 32 board-certified physicians: eight from each of three subspecialties—cardiology, haematology, and infectious disease—and eight general practitioners who did not subspecialise.
The participant physicians were asked to diagnose four patient cases that satisfied three conditions. First, the correct diagnosis belonged to one of the subspecialties of interest, plus a fourth subspecialty not represented among the experts. Second, no case was inherently misleading. Third, that no case was inherently easily diagnosed into one specialty exclusively. For each case, participants received a two-to five-page abstract prepared by an expert clinician based on the actual patient charts. The abstracts included all the salient history, physical examination findings, laboratory results, and radiological and other diagnostic studies.
The goal was to examine whether physicians with a given specialty have a bias in diagnosing cases outside their own domain as being within their speciality. The short answer was yes and confirmed the experimental hypothesis that specialists try to “pull” cases toward their discipline. Participants generated considerably more diagnostic hypotheses within their domain of expertise than outside their domain and assigned a higher probability to hypotheses within than outside their domain.
A study from 2019 by BMJ Quality & Safety indicated that each year in the U.S., over 12 million adults receive a misdiagnosis, that is 1 out of 20 adult patients.
While the use anonymous patient files my indicate physician bias in diagnosis, there is also the secondary, probably under-appreciated reason for the specialist/diagnosis bias phenomenon, the patient’s description of what is wrong with them. When a patient presents a doctor with symptoms of unknown origin, they are likely to order several diagnostic tests including some related to his or her specialty.
Any abnormal values from the tests, especially from ones they are familiar with, are likely to shape the diagnosis. But that raises a second problem, when a body part or bodily process is damaged through illness or injury, other parts or processes may make compensatory changes that will equally show up on the tests. For example, people with a leg injury may change how they walk in order to reduce stress on the leg, which in turn may lead to a tightening of back muscles and pain in the hips, hence, a knee injury may lead to back pain.
Another possible example would be in response to kidney failure, the respiratory rate decreases and there is diminished reabsorption of bicarbonate. If the kidney is damaged, the remaining kidney undergoes compensatory growth. An abnormal reading may not be indicative of the source of the problem, but doctors who focus on tests related to their specialty may allow abnormal results to shape their diagnoses.
For uncomplicated diagnoses a single diagnostician is sufficient. But if there’s any uncertainty, it’s probably wise to have at least two doctors from different specialties. Then, abnormal test results caused by a dysfunction elsewhere in the body will be less likely to shape diagnoses. Experienced diagnosticians are unlikely to be misled by abnormal test results, but the less experienced may be susceptible. The onus is on the doctors to carefully document cases where an abnormal result is found to be secondary to a dysfunction elsewhere, then future diagnosticians will be less likely to make an incorrect inference from a similar abnormal value.
This raises the question of how often a misdiagnosis is critical and how far is the misdiagnosis large or small in effect. Results published in Clinical Orthopaedics and Related Research show that while the number of misdiagnosed cases in the U.S. is high, the evidence of harm is low. Philip Peters examined 20 years of evidence on the outcomes of malpractice claims and found that physicians win approximately 85 percent of the jury trials with weak evidence of medical negligence, and even 50 percent of the trials in cases with strong evidence. Between 80 percent and 90 percent of the claims rated as defensible were dropped or dismissed without payment. There are serious cases that result in death, but they comprise approximately half a percent of all misdiagnosed cases.
Doctors do get the diagnosis wrong at times, and in serious cases it has a tragic outcome. However, on the weight of the evidence, doctors at least approximate a correct diagnosis to the satisfaction of the courts. While improvements would help, it is also the case that a patient-explanation free approach to diagnosis would also improve the outcome.
Words: Prof Fred Leavitt.
Prof Fred Leavitt has a PhD from the University of Michigan, has lectured psychopharmacology and research methodology at different Universities in the US and abroad for over 40 years, and is the author of eleven books, among the If Ignorance is Bliss, We Should All Be Ecstatic, reviewed by I-M Intelligent Magazine HERE.
Opening picture by Parentingupstream, Pixabay.