Several studies have shown that diagnostic mistakes—diagnoses that are missed, wrong or delayed—are the most costly, dangerous and deadly errors made by doctors. 

In fact, in a 2013 study, researchers from The Johns Hopkins University School of Medicine found that diagnostic mistakes cause more permanent disability and death than any other type of medical errors, including more than medication-related and surgical mistakes combined.

Now: The same researchers have conducted a recent study funded by the Society to Improve Diagnosis in Medicine and published in Diagnosis. It finds that three types of disease account for about 75% of all diagnostic errors resulting in permanent disability or death…and there are five specific diseases in each of the three groups that most often cause harm. 

To learn more about the latest study and what it means for patients, Bottom Line Health spoke with David E. ­Newman-Toker, MD, PhD, lead author of the study mentioned above.

The “Big Three” and “Top 15”

Based on previous studies from Dr. Newman-Toker and his colleagues, diagnostic errors that cause death or serious disability affect at least 80,000 to 160,000 patients every year in the US. Dr. Newman-Toker now believes that number is probably ­underestimated by fivefold. Many of these deaths and disabilities can be prevented. 

To find out what diseases are most frequently missed, researchers in the latest study reviewed more than 11,000 diagnostic error–­related malpractice claims that resulted in more than $2 billion in payouts over 10 years. They found that about 75% of serious diagnostic errors were attributed to three major disease categories. 

The researchers labeled these the “Big Three.” Among the malpractice claims reviewed, the researchers found cancer (38%) to be the most common cause of serious harms, followed by vascular events (23%) and infections (14%). Within these three categories, lung cancer, stroke and blood infection (sepsis), respectively, were the most common causes of serious harm or death due to diagnostic mistakes. 

Other common types of cancers causing harm included breast, colorectal, prostate and melanoma. In the vascular category, the other common conditions causing harm were heart attack, venous blood clots (thromboembolism), aortic aneurysm and arterial thromboembolism. Brain, spinal, lung (pneumonia) and heart infections (endocarditis) filled out the infectious diseases. Together, these diseases make up the “Top 15.”

The Where, Who and How

The study found that diagnostic errors in outpatient settings, such as doctors’ offices and clinics, were disproportionately missed cancers, while diagnostic errors in the emergency room or hospital were mostly missed vascular events and infections. 

Four types of doctors were most likely to make diagnostic errors— internal medicine specialists, emergency room doctors, family practitioners and radiologists. Over 85% of cases included clinical judgment mistakes, which were by far the most common underlying causes. These errors included not ordering or delayed ordering of diagnostic tests, not considering alternate diagnoses, missing signs and symptoms, not consulting with medical specialists and misinterpreting an imaging study or pathology sample.

What This Means for You

Knowing the dangers of missed diagnoses and when they are most likely to occur can help you to avoid being a victim. For doctors, the findings of this study show where gaps in knowledge occur, where better training, and perhaps the addition of computer-based diagnostic tools, and better access to specialty consultations would be most valuable. For example, the biggest risk areas for harm from diagnostic mistakes are stroke diagnosed in the emergency room, sepsis diagnosed in the hospital and lung cancer diagnosed in primary care settings.

How you can avoid misdiagnosis…

  • If you have signs and symptoms of a new medical problem, go to the website of the Society to Improve Diagnosis in Medicine, The information here can help you prepare for your doctor appointment. Important: Before your appointment, write down all your symptoms on one sheet of paper that you can leave with your doctor. This will give him/her more time to consider your diagnosis.
  • Ask your doctor to explain the reasoning behind his diagnosis. If he tells you not to worry about it or brushes you off, get another doctor or another opinion. 
  • If your doctor has ordered a diagnostic test, follow up to get the results. Do not assume that no news is good news.
  • If you are not getting better after starting treatment, do not ­assume that the particular treatment is wrong—the diagnosis may be wrong. Ask for a new appointment to discuss your concerns, or get a second opinion.

Important: Diseases may get missed when symptoms aren’t “textbook” or they mimic something more common. Examples: Stroke causing dizziness can look like an inner-ear infection…and early sepsis can look a lot like a viral infection. Be careful if the doctor seems to take the simple path without considering or ruling out dangerous causes of your symptoms. 

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