Inadvertent Therapeutic Trial
The definition of a therapeutic trial is when the diagnosis of a particular condition is established by a trial of specific treatment.
Not that this lets physicians off the hook for making the diagnosis. You still have to do a history and physical. In fact, you basically have to make the diagnosis first, then use the treatment to see if you're right. In everyday practice, the application of a therapeutic trial is quite limited. It is not valid, for example, to give penicillin to everyone with a sore throat and see if they get better. The regimen has to be very specific to the condition; it's the only way to be sure it's really the treatment that's having the observed effect, if any. There are very few conditions that have treatments specific enough to qualify as a true clinical therapeutic trial.
But what happens when you give someone a medication to treat one thing, and something else happens?
A patient with longstanding irritable bowel symptoms and a known allergy to cats (no relationship between those two conditions) broke out in really bad hives from inadvertent exposure to cats, and was treated with steroids. Three months later, she called to tell me that while she was on the steroids and for about two months afterward, her IBS symptoms resolved completely. Now they were coming back.
Oops! Perhaps her GI symptoms weren't due to irritable bowel syndrome -- something you wouldn't expect to be affected by corticosteroids -- after all. Perhaps she really had something completely different, like inflammatory bowel disease (Crohn's disease or ulcerative colitis) or celiac disease. Sure enough, her tissue transglutaminase antibodies came back elevated, indicating celiac. She's off to the gastroenterologist for confirmatory biopsies, followed by lifelong avoidance of gluten. The good news is that her GI symptoms should resolve completely (again). The bad news is that she's at increased lifetime risk of assorted other conditions like diabetes and cancer, although some of these can be lessened with the gluten-free diet.
All because she broke out in hives.
(And noticed the change in her IBS symptoms and called me.)
(And because I knew what to do.)