From Lewis Blevins, MD, Neuroendocrinologist, Medical Director of the California Center for Pituitary Disorders, Professor of Neurological Surgery at UCSF and PWN cofounder – I’ve seen several patients recently who illustrate one of the basic, yet seemingly forgotten or ignored, principles of the practice of medicine. It’s called a differential diagnosis. Put simply, it’s a list of diagnostic possibilities that must be considered at the outset of a quest to evaluate and diagnose an ailment. The list may be generated in a physicians mind upon hearing a complaint. It might be pruned down to a few things that seem more likely based on answers provided to a few simple questions and even further based on exam findings. Laboratory and other diagnostic tests may narrow the focus and even confirm a suspected diagnosis.
One of my patients presented with erectile dysfunction. Instead of developing and working through a differential diagnosis he was simply treated with medications to improve erections. The drug did not help matters. A few years later he was found to have low testosterone levels. Instead of recognizing this was on the list of the differential diagnosis for erectile dysfunction, and recognizing a more narrow differential diagnosis must be considered, he was simply treated with testosterone. Some eight years later his physicians stumbled onto a diagnosis of a pituitary adenoma and his prolactin levels was elevated. His tumor was invasive and surgical removal was not an option.
What was the differential list? For the erectile problems it included: low testosterone, psychological stress or depression, neuropathy, peripheral vascular disease, medications. A careful history , medication review and testosterone levels would have set the course for a diagnosis a decade earlier.
How about the differential for the hypogonadism? It included a number of conditions like depression, stress, chronic illness, alcoholism, testicular problems and various hypothalamic and pituitary disorders. Again, a careful history and physical would have excluded these. Measures of LH and FSH would have enabled the doctors to discern whether the hypogonadism was primary, related to testicular issues, of central related to hypothalamic or pituitary issues.
In my patient his LH and FSH levels were low normal and the total and free testosterone levels were low normal. This pattern suggested a differential diagnosis of hypothalamic or pituitary disorders, chronic illness or stress, etc. a prolactin and a pituitary MRI would be indicated. As mentioned, he was found to have an invasive prolactinoma. Treatment had been delayed for a decade because a differential diagnosis was not entertained at the outset when he presented with erectile dysfunction.
I see a lot of patients just like this one. Other common scenarios are equally disappointing. They result from treating symptoms and signs as the disorder that’s needs to be remedied and not in trying to understand why the conditions are manifest in the first place. Physicians have either forgotten this lost art of the differential diagnosis, don’t have the time for it, don’t wish to delay treatment, or start with a narrow differential in the first place. Granted, if a guy has erectile dysfunction a pill may be a quick fix for a doctor who has a waiting room full of patients and is running behind. But it’s the incorrect way to proceed. Perhaps the availability to treat symptom and signs and patients perceptions that leaving with a pill is a reasonable conclusion to a visit are a part of the problem.
I like to refer to some of the diagnoses, such as hypogonadism, as gateway or presenting diagnoses. Almost all gateways lead to something causal.
I’ve seen women with absent or irregular menses treated with oral contraceptive pills in lieu of a work-up that often, years later, reveals they had a pituitary disorder. Some patients with diabetes mellitus and hypertension treated with multiple medications for years are later diagnosed with hypercortisolism. In most cases, the differential diagnosis was not even considered as the health care team went to work to control blood glucose levels and blood pressure. I could not tell you the absolute numbers of patients who had sleep apnea or carpal tunnel syndrome as first manifestations of acromegaly that was diagnosed until 10-20 years later as a differential diagnosis was not considered upon presentation. The list of examples could go on and on.
One thing is very clear, physicians and patients believe that earlier diagnosis and treatment are better in the long run. While we may need to do a great deal of education regarding disease states, I believe that increasing an awareness of the need for physicians to get back to the basics of the differential diagnosis and appropriate investigations is essential to meet the goals of early diagnosis.
What can you do?
It’s simple. Ask your doctors what might be causing the diagnosis they’ve made and especially if it is a gateway diagnosis like osteoporosis or any of the others mentioned above. There are plenty more examples. Do your research. Go to AI and ask simple questions such as “What are the causes of erectile dysfunction?” “What can cause my periods to stop?” “What can cause me to have diabetes and hypertension?” Print the search results and discuss them with your doctor. Recognize that not all of the tests you might see and learn about in your search are warranted. Also, some tests will be absolutely not needed. Medical reasoning based on answers to questions, exam findings, and patterns in laboratory tests can obviate the need for other tests. For example, if the patient mentioned above had had high LH and FSH levels we would have considered the differential diagnosis of testicular disorders. He would have not needed a prolactin level and MRI studies.
This notion of a differential diagnosis is not all that unfamiliar. For example, mechanics use this way of thinking as they evaluate problems that causes car troubles. An engineer might approach structural failures in the same manner. A farmer might do the same when evaluating a low crop yield. The differential diagnosis comes from within. It seem a natural process of analysis or “narrowing it down” for the human mind. It’s innate. Make sure your doctors are using their brains wisely.
Image by Tamim Ahmed from Pixabay
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