Diagnosing By Excluding

What's left after all the testing dust has settled?

A friend wrote a note about a relative with a problem - with doctors. "Why is it", wrote the complainant, "that doctors who are IN PRACTICE are STILL PRACTICING?

The occasion was one in which a child in her family had been misdiagnosed as having a functional or "conversion" disorder causing recurrent vomiting. "Conversion" is a modern term replacing psychosomatic or hysterical, and it is more than important - it is vital - not to make this diagnosis until all other possibilities are excluded. (Note: For the sake of purists, we must say that Conversion Disorder symptoms generally are neurologic, such as paralysis or loss of a special sense.)

In spite of all of our advances in technology and in medical knowledge it is still not possible to diagnose perfectly all the time. What is done is a process of proceeding through a list called a differential diagnosis, a roster that may be very long in some cases, eliminating those answers that don't fit. The poor fit may be detected by taking a good history of the problem, by doing a good examination of the patient, or by appropriate testing and consultation.

After all this, there may still be cases which simply don't coincide with a specific disorder which can be seen, felt, or pinned down by an abnormal test. Sometimes this leaves us with (fanfare) Conversion Disorder, and we have arrived here by excluding all the readily diagnosable other possibilities. In that last sentence, the word "all" is relative. It's more accurate to say, "All we could think of."

Two things may happen after we've exhausted all the procedures and discarded most of the diagnoses. The first is relatively good - patients may just stop feeling unwell, the symptoms go away, and everyone thinks, "Whatever that was, it's the worst one I ever saw, and I hope I never see it again."

The second outcome is not so good. Sub-outcome A will be that the victim is shoehorned into one of the categories labeled "Hard to identify" such as fibromyalgia / chronic fatigue, or, more commonly, depression cum conversion disorder. Sub-outcome B is that the patient will be referred in turn to several consultants, each of whom will attempt to classify, correctly or not, the problem patient as belonging in one of their familiar diagnoses.

This is the practice of medicine, and it's performed by people with terrific educations, training and experience.

Actually, there is a third outcome. Finally something absolutely diagnostic (a unique rash or a really specific test that hadn't been thought of before) takes place and it's a sudden light in the darkness. The doctor cries, "Eureka! This is XXYZ, and we'll begin treatment immediately." The patient or his family cries, "You boobies! why didn't you think of this earlier?"

The reputation of a hard working and honest, well trained physician is often badly skewed by such an occurrence, and there is often no good outcome for her or him. An apology to the patient or family for not thinking of XXYZ may be met with hostility, and if an attempt is made to excuse the oversight ("Well, that's just too uncommon to be considered by a rational person", etc.) there may be hell to pay. Or the comment, "Doctors! When are they going to stop practicing and start practicing?"


In spite of general excellence in our medical system this hostile scenario isn't uncommon, and it won't go away without lots of help. The best help is a good open relationship with patients and families, in which a provider allows them to see and understand everything that's going on, and to make comments or ask questions anytime something perplexing happens.

This used to be the medical model but we don't see it in use much anymore. In a healthcare cooperative, it will be possible to regain what has been misplaced. As the saying goes, "Ask me about that sometime."