“Fibromyalgia” is our odd label for unexplained widespread chronic pain and malaise. It is still routinely and incorrectly called a diagnosis of exclusion. I did so myself, until I was corrected in early 2021.
Although technically wrong, the term “diagnosis of exclusion” is also a seed of truth in a practice-vs-theory way. It’s useful to break this down. And “wastebasket” diagnosis is also worth understanding (for entirely non-technical reasons).
Inclusion versus exclusion
A “diagnosis of exclusion” is basically a diagnosis achieved by a process of elimination, and that seems simple enough, but it’s not a well-defined concept. By its very nature it tends to only be applied at the edges of medical knowledge, where many of us live, and things are kind of a mess out there.
What is clear is that fibromyalgia is officially a criteria-based diagnosis these days. We know enough about the condition that specific features are required for diagnosis (Wolfe 2016). It is formally defined by what is wrong, not by what isn’t. So it’s a diagnosis of inclusion, not exclusion!
In practice, however, fibromyalgia is often still treated like a diagnosis of exclusion, something that is brought up only when most other possibilities have been eliminated.
What’s so bad about arriving at “fibromyalgia” by a process of elimination?
You might never get there! Or you might eliminate something you shouldn’t along the way.
Fibromyalgia can and does co-exist with similar conditions (e.g. rheumatoid arthritis). And so it would be a serious mistake to consider fibromyalgia only in their absence — you might miss the fibromyalgia that is also going on! Or you might erroneously rule out something like rheumatoid arthritis in your eagerness to explain the symptoms with fibromyalgia.
And then there’s “wastebasket” diagnosis
“Wastebasket diagnosis” is basically a crappy diagnosis of exclusion: a careless and ignorant process of elimination, instead of an earnest and educated one.
Wastebasket diagnosis is defined by obnoxiously non-medical motives. What motives? At best, it’s a diagnosis given as a pacifier, a kind of diagnostic placebo — well-intentioned but misguided. At worst, it’s a way to just create the appearance of a diagnosis, while actually dismissing the patient, and often justify passing the buck to another physician.
It’s the diagnostic equivalent of pretending to throw a ball for a dog: “Go get it, boy!”
Sadly, “fibromyalgia” is constantly diagnosed this way in the real world.
Don’t rule out exclusion yet!
Exclusion still has a role to play for some good reasons. In the full fibromyalgia article, there’s more detail about lots of messy overlap between “criteria-based diagnosis” and “diagnosis of exclusion.” Here’s the gist, though: a certain amount of narrowing things down is both necessary and inevitable in tricky diagnosis. Accidentally eliminating things that shouldn’t be, or failing to eliminate what should be, is just an occupational hazard that can’t be entirely … eliminated.