This is a Chapter from my forthcoming book, Patient Safety – Protect yourself from Medical Errors.
Diagnosis plays a central role in medicine, and making the right diagnosis is pivotal in helping the patient to get the right care. Making a diagnosis is a complex exercise, because patients don’t come with labels saying I suffer from so-and-so. There is probably no task more challenging for a doctor than making the correct diagnosis.
The doctor needs to be a detective in order to figure out what’s wrong, and it’s because there is so much that we still have yet to learn about the human body, that diagnosis is still a very uncertain art. It takes considerable clinical acumen to make the right diagnosis, which is why one in every ten diagnoses is wrong.
Diagnostic error is the leading cause of medical malpractice claims in the US, and is estimated to cause 40,000-80,000 deaths annually. It’s because misdiagnosis can do so much harm, that we need to ensure that the diagnostic process is timely, accurate, reliable, and efficient if we want to make medical care safe.
When Do Diagnostic Errors Occur?
A diagnostic error occurs when either the diagnosis is wrong, missed or delayed. The cause of diagnostic error is often multi-factorial, and it could be a result of:
Cognitive Errors- A mistake in the doctor’s thought process, perhaps because he is too rushed
System Errors- Because of the lack of communication, as a result of which an abnormal lab result is overlooked
A Combination of both
A diagnostic error is more closely associated with some specialties than others, such as radiology, geriatrics and emergency medicine. They are common in the ICU ( Intensive Care Unit) as well, where patients have multiple complex problems. Interestingly, it is not only the rare disease that is the subject of diagnostic error; it is the misdiagnosis of common diseases such as heart attack, cancer and stroke which causes the most harm.
Doctors are taught to follow a disciplined process in order to make the right diagnosis. This involves collecting information from the patient by taking a history, doing a clinical examination, and ordering lab tests. The clinical data then needs to be analyzed and processed. The systematic method that doctors use to come to the right diagnosis is called differential diagnosis.
The doctor makes a list of possible diagnoses in order of probability, and then tests the strength of each diagnosis by asking further detailed questions, ordering more tests, or referring the patient to specialists. A differential diagnosis checklist helps physicians avoid the most common cause of diagnostic error – failure to consider the correct diagnosis as a possibility. Ideally, a number of potential diagnoses will be ruled out as the investigation progresses, and only one will remain at the end. Of course, given the uncertain nature of medicine, this is not always the case.
Technology can also aid doctors to help minimize diagnostic errors . Medical digital databases like Watson @ http://www.ibm.com/smarterplanet/us/en/ibmwatson/ and Isabel @ http://www.isabelhealthcare.com can be utilized intelligently to boost the doctors’ diagnostic accuracy, by serving as diagnosis support systems. They do not replace the doctor, but do help to remind him to consider all possibilities, so he does not overlook a particular disease.
Why does misdiagnosis occur?
Since the doctor has to make the diagnosis, there are many ways in which he can err:
Most doctors know only the common diseases-There are more than 20,000 human diseases, and most doctors don’t know about the rare ones, which is why these are often missed.
Different doctor skill levels-Not all doctors are alike, and while a general practitioner is well versed in common diseases, a specialist would know a lot more about the rare diseases(in his specialty).
Doctor bias-All doctors are human and have biases. If they see a certain disease frequently, they tend to diagnose it frequently, and this might result in an error if the patient does not have that disease, but something with similar symptoms.
Saving you money-Some doctors will avoid tests, because they don’t want you to pay extra for tests which are not likely to be helpful. This works well for the majority, but can result in a misdiagnosis for the small percentage that might have a rare disease.
Lack of time- It really is quite sad how little time a doctor will typically spend with a patient. In reality, doctors have to shoot from the hip; although they’ll hit the mark with most common diseases, they can get tricked by rarer conditions.
Some symptoms are hard to analyze-Medicine can be complex and the human body can fool even the smartest doctors.
Laboratory tests and imaging studies
The various medical tests that are used to confirm or rule out diagnoses can also sometimes fail. They are useful tools, but are not perfect and the things that can go wrong are:
Human errors- Samples could get contaminated or mixed up, or the test procedure might be done improperly-for example, if the laboratory technician is unqualified , or the lab is poorly equipped. This can be a major problem in India, where quality control is often lacking.
False positives and false negatives- All laboratory tests have known conditions under which they fail. They can either give a false positive, wrongly indicating that you have a disease when you don’t; or a false negative, wrongly indicating that you don’t have a disease when you actually do. Either way will get you the wrong diagnosis.
Misinterpretation-Many tests rely on the expertise of the doctor doing them-for example, the skill of the pathologist in analyzing the tissue biopsy he receives. Errors are rare, but they can occur. Thus, errors made by radiologists in interpreting scans fall into two groups:
Perceptual errors (missing what is on the film)
Cognitive errors (seeing what’s on the film, but failing to attach significance to it)
It may seem unfair to hold a patient responsible for a wrong diagnosis, but what the patient does (or does not do) can contribute to a wrong diagnosis as well. This is how patients sometimes end up shooting themselves in the foot.
Self diagnosis-The most likely way for a patient to contribute to a misdiagnosis is attempting to diagnose themselves, without professional medical advice.
Not reporting symptoms-Sometimes patients don’t tell their doctor everything, either because they are embarrassed, or they feel that it’s minor , and not worth mentioning.
Failure to perform the ordered tests- In some cases, patients don’t get diagnostic tests done, even when a doctor has ordered the tests. This can occur due to oversight, financial constraints, complacency, laziness or embarrassment.
What can patients do to reduce diagnostic error and harm?
See a doctor- A majority of the diagnoses made by doctors are correct , and are far more likely to be accurate than your own. Never self-diagnose based on what you have read on the internet, in books, or gathered from amateur advice. Doctors are trained to see signs that patients don’t.
See a specialist- A trained specialist is even less likely to make a wrong diagnosis than your family doctor.
Ask for a diagnosis- Ask your doctor to explicitly name his diagnosis. Sometimes the doctor may not tell you what the name of the condition they suspect is, not because they want to keep you in the dark, but perhaps because they don’t want to scare you with a serious sounding name. Other doctors feel that patients won’t understand the diagnosis anyway, or that they don’t want to know.
Ask questions- It is hard to assess the accuracy of your diagnosis unless you understand what it is, and the basis on which it was made. Exactly what is the diagnosis? How sure is your doctor? Are any other diagnoses possible? What other diagnoses has your doctor ruled out? What other related diseases are possible? Which ones have been tested for or ruled out?
Dr Jerome Groopman, the author of How Doctors Think, suggests asking the following 3 questions:
What else could it be?
Is there anything that doesn’t fit?
Is it possible I have more than one problem?
Get a second opinion – Getting the opinion of two or more doctors reduces the chances of a wrong diagnosis. If the two diagnoses match, then the chances of a wrong diagnosis are much lower. And if they don’t match, then this is a puzzle that needs to be solved in order to get to the correct diagnosis. Many online second opinion services allow you to consult with world-renowned specialists from the comfort of your home. Lots of health insurers also offer their customers a free second opinion service, to help them make sure that their diagnosis is correct.
CrowdMed( http://www.crowdmed.com) uses the wisdom of the crowds to help solve diagnostic puzzles. It is an online medical crowdsourcing platform where you can submit information about your symptoms, medical history, tests, scan results and other pertinent data. This community of “medical detectives” then suggests diagnoses, and CrowdMed’s algorithms aggregate these medical differentials and distill them down to a probable list of diagnostic suggestions for you . This has an extremely high degree of accuracy, and is well worth exploring, especially when your doctor is stumped.
Step back and take a second look
Repeat the laboratory tests and scans- To reduce this risk, you can repeat the same test. This reduces the likelihood of a simple laboratory error or administrative mix-up, since this shouldn’t happen twice.
Run different tests- If there are multiple diagnostic tests for your disease, consider having another type of test done.
Use a different laboratory- If you don’t trust your test results, you might want to get them repeated at a different laboratory.
Research your disease- The best way to feel confident in your diagnosis is to understand how it was made, by being well-informed. Knowledge is power! You can use an online symptom-checker to help you make sense of what the diagnostic possibilities are. The trouble with many of these is that they may needlessly scare you; so you have to resist jumping to the conclusion that you have an incurable medical disease when you go online.
Patients are often the key to the right diagnosis
Even though patients don’t have the medical tools and diagnostic skills that doctors do, they are the experts on their illness. An accurate medical history is the most valuable tool in helping the doctor to come to the right diagnosis, and often is far more valuable than expensive tests and esoteric scans.
It was Sir William Osler who said – “Listen to your patient, he is telling you the diagnosis.” Sadly, doctors are often too busy to take a proper history, and patients are often too disorganized, as a result of which they may fail to provide the doctor with valuable medical clues. It’s important that patients take responsibility for helping the doctor to make the right diagnosis, especially when they have a problem which has stumped their doctor, by being better organized, and writing down their story in a structured format, so it’s easier for the doctor to review this.