When is it inappropriate to enter the long tail?

One of the challenges of the long tail is knowing when and when not to enter it. In Bob Wachter’s recent post on patient centered care he recounted a tragic case of hyperparathyroidism misdiagnosed as leptospirosis. Rather than thoughtful consideration of long tail diagnoses as DB has described, this may be an example (combined with some serious system problems) of an impulsive and inappropriate leap into the long tail ignoring, among other things, the maxim that “common things happen more often.”

Why did the doctors make the leap? We don’t know, but Wachter thinks he’s seen the dynamic before, and relates this story:

When I was a UCSF resident, one of the community-based physicians admitted a patient to me. This physician, may he rest in peace, had a well-deserved reputation for clinical incompetence. “Bob,” he said in his glad-handing way, “I think this guy has amyloidosis.” I was impressed: amyloid is an unusual disorder with a variety of fairly specific organ system derangements. Was it possible that Dr. X had analyzed the signs and symptoms and made this diagnosis? That seemed farfetched. “What makes you say that?” I asked, genuinely interested. “Well, I saw a guy a few months ago who was really, really sick, and he turned out to have amyloidosis.” I’m guessing that some hapless Irish doc saw one serious case of leptospirosis, and he'll keep making that diagnosis until a new case happens along or he retires, whichever comes first.)

I think I’ve seen this on occasion. Someone has a pet diagnosis, an uncommon disease, and leans on it to explain virtually every really sick patient with mysterious signs and symptoms. I don’t know of a label for this sloppy cognitive shortcut, so maybe we should call it the “pet diagnosis heuristic” or the “impulsive leap into the long tail.”