I might have difficulty convincing some physicians or medical insurance CEO's of the validity of the maxim stated above, but for anyone who has been misdiagnosed and subsequently suffered through months or years of innappropriate medical treatment, the maxim is for the most part, true. Due to the compartmentalization and politicization of modern medicine, awareness of the high costs of misdiagnosis, both monetarily and in terms of human suffering, may be sorely lacking.
Crucial to achieving a correct diagnosis is an understanding not only of the complexities of human illness, but also of the limitations and deficiencies inherent in all diagnostic tests.
For the layperson, it is important to be aware of just what sort of definitive conclusions can be drawn from each type of test. A physician that is subject to incentives or disincentives regarding the requisition of diagnostic tests may try to convince the patient that a certain test definitively rules out certain conditions, when in fact this may not be the case. It is crucial for the physician and the patient to understand the fallibilty of each test, and to be aware of the potential for false positive and false negative results.
No test is completely accurate. Sometimes a test result is incorrectly abnormal in a person who doesn't have the disease (a false-positive result). Sometimes a test result is incorrectly normal in a person who has the disease (a false-negative result). Tests are rated in terms of their sensitivity (the probability that their results will be positive when a disease is present) and their specificity (the probability that their results will be negative when a disease is not present). A very sensitive test is unlikely to miss the disease in people who have it. However, it may falsely indicate disease in healthy people. A very specific test is unlikely to indicate disease in healthy people. However, it may miss the disease in some who have it. Problems with sensitivity and specificity can be largely overcome by using several different tests. For example, a person who tests positive for AIDS with a very sensitive test is retested with another more specific one.
It is important to understand that a diagnostic test is often much like a snapshot of bodily processes. In many cases, especially where pain and discomfort is transient and irregular, a test may appear normal even though there is a medical disorder present. Much like taking your stumbling car to the mechanic, only to have it work flawlessly while there, many medical disorders are transient, unpredictable, or sporadic in nature. It is often difficult to exactly simulate the conditions under which the malfunction occurs while performing the diagnostic test.
Another obstacle to achieving a correct diagnosis is often the unwillingness by the physician to request appropriate diagnostic testing, usually due to cost considerations. You will often hear physicians say "that test is too expensive", or "that test won't be necessary", or "you'll have to wait six months for the CT scan due to the long waiting list". These statements are often made without due consideration being given to overall cost implications of misdiagnosis.
In our daughter's case, a simple 10 minute abdominal ultrasound performed early on may have saved months of hospitalization, psychotherapy, and nutritional counselling, not to mention the terrible suffering she went through. The cost of her operation was a small fraction of the cost incurred from the inappropriate treatment due to misdiagnosis.
Another factor in achieving accurate diagnoses is the acknowledgement of the complexities of human illness. Many diverse ailments have similar or overlapping symptoms. Some illnesses manifest themselves differently in each person. Some patients experience few of the classic symptoms, while others experience symptoms not normally associated with that particular disease. Some medical disorders will precipitate a cascade of complications, which can make interpretation of the symptoms difficult.
Here's how the diagnosis of a digestive disorder in a patient meeting all the diagnostic criteria of AN may be missed:
Let's say the patient is a 17 year-old female, named Susan, who has been restricting food intake, and exercising excessively, to the point where menses has ceased and severe malnutrition has given her an emaciated appearance. She presents with bradycardia, constipation, lanugo hair, occasional abdominal pain, and claims to want to lose more weight. She also occasionally vomits after meals, has been using laxatives excessively, and has been very depressed. She has been a very fussy eater for most of her life.
Unknown to her, her parents, friends, the physician, and her therapist, her gallbladder has a very small cyctic duct which tends to kink occasionally when she is sitting up. She has gradually developed cholecystitis, which is the real reason she has difficulty eating, as well as trouble absorbing fats and protiens. She often feels nauseated after eating.
Susan is a shy girl, and so at first doesn't mention to the doctor that she's having trouble with bowel movements, or that she occasionally gets terrible bloating and stomach pain after she eats a fatty meal. She has also recently become a vegetarian, and prides herself on not eating any meat products.
She is lucky enough to have a good doctor, who knows he has to rule out all medical illness before mental illness can be diagnosed. He sends her for blood tests, an upper GI series, and an abdominal ultrasound. The blood tests come back normal, except for some elevated liver enzymes and high carotene levels. The liver enzyme abnormalities are attributed to malnutrition. The high carotene levels are assumed to be due to her eating a lot of carrots, since she is a vegetarian.
The upper GI series appears normal, and the ultrasound showed slight gallbladder wall thickening, but no evidence of gallstones.
Suspicious of the enlarged gallbladder, he orders a HIDA scan, which shows a gallbladder ejection fraction of 62%. The test is performed in the supine position, as always. The ejection fraction is not viewed as abnormal, so he concludes that the gallbladder is working fine.
Concerned about the constipation and vomiting, he orders a barium enema, which shows nothing out of the ordinary. The doctor tells Susan, "there doesn't seem to be anything wrong with your digestive tract, so I'm going to see if I can get you into the local eating disorder program. They'll be able to help you."
Unfortunately for Susan, the tests missed the real problem, which was the cholecystitis. If her doctor had ordered an erect CCK test, her cholecystitis may have clearly shown up, allowing proper medical treatment and recovery to ensue.
Susan is also convinced she has an eating disorder, since she isn't aware that something is physically wrong. Her doctor assumed that the tests definitively ruled out any medical disorder, which was an incorrect assumption.
Of paramount importance in the effective diagnosis of any medical disorder is to guard against making assumptions that presenting symptoms are only due to the suspected illness, or that diagnostic tests are not prone to inaccuracies. Realizing this, correct diagnosis and successful treatment of the underlying disorder can be achieved.