Using Different Fibromyalgia Criteria Affects Prevalence Estimates

The Study

Dr. Wolfe’s team wanted to compare the prevalence of fibromyalgia as assessed by the 2016 modification of the 2010/2011 criteria with the prevalence assessed by the AAPT criteria, and clinical aspects of cases diagnosed according to both sets of criteria, as well as specific criteria items that contribute to diagnosis.

The researchers randomly selected 2,532 subjects in the general German population—
of whom 1.1% self-reported diagnosed fibromyalgia—and applied both the 2016 modified criteria and AAPT criteria. Under the 2016 criteria, the prevalence of fibromyalgia was 3.4%, compared with 5.7% under the AAPT criteria.

Dr. Clauw

Compared with participants diagnosed via the AAPT criteria, those diagnosed by the 2016 modified criteria had more multi-site pain, higher scores on the WPI and PDS, and a greater psychological symptom burden.

Of the 1.1% of subjects who self-reported a previous fibromyalgia diagnosis, 44% met the 2016 modified criteria, vs. 47.5% who met the AAPT criteria.

The researchers write that the AAPT cri­teria selected individuals with less symptom severity and fewer pain sites. They add that the 2016 modified criteria provide a general severity measure, while the AAPT criteria do not. If head and face, chest, abdomen and pelvic pain were excluded from the AAPT criteria, they would have produced about the same prevalence as the 2016 modification, the paper says.

Both sets of criteria rely on the judgment of clinicians, the paper notes. It suggests clinicians include the criteria used to diagnose fibromyalgia in medical reports and use the PDS scale, regardless of the criteria used. “The PDS looks at how many bad, troublesome symptoms you have, not whether you have fibromyalgia,” Dr. Wolfe says.

Using the PDS removes borderline diagnoses and allows recognition of both flares and improvement, according to the paper.

Editorial

In the editorial, Dr. Clauw, a co-author of the 2010 ACR criteria, subsequent modifications, and the AAPT criteria, says that although the researchers appropriately found neither set of diagnostic criteria superior, a “dizzying array” of other fibromyalgia criteria exist for diagnosis and screening. Each set of criteria “identifies slightly different subsets of individuals, resulting in only modest agreement between the criteria when applied in practice or research.”

Either set of criteria suffices for a diagnosis of fibromyalgia, according to the editorial. But Dr. Clauw prefers the 2016 modified criteria for clinical use because they can be scored as a continuous quantitative measure.

The editorial notes that Dr. Wolfe was the first to suggest the degree of suffering from symptoms associated with fibro­myalgia is more important than meeting specific diagnostic criteria. “Everyone has a little ‘fibromyalgianess,’ and some people have a lot,” Dr. Clauw said in the editorial.

Another advantage of the 2016 modified criteria is that it easily identifies chronic pain patients with comorbid sleep, fatigue and sleep problems, which often have effective treatments. The 2016 modification also includes continuous quantitative measures to recognize fibromyalgia symp­toms in patients who do not meet diag­nostic criteria but can still benefit from established treatments, the editorial adds.

“Practitioners should think of fibro­myalgia along the lines of rheumatoid arthritis or gout: if you wait until it is too advanced to diagnose and treat, the damage may be done,” Dr. Clauw said in the editorial.

The editorial cites research that concludes fibromyalgia pain is due to nociplastic pain, which arises from no obvious injury or inflammation, but from changes in how the brain works. Many researchers think nociplastic pain mechanisms play a role in rheuma­toid arthritis, tension headache, irritable bowel syndrome and other conditions that sometimes overlap with fibromyalgia. In 2016, the International Association for the Study of Pain recognized nociplastic pain as a new pain category, alongside nociceptive and neuropathic pain.

While Dr. Clauw sees fibromyalgia as more of a neurological problem, Dr. Wolfe believes it arises mainly from psycho­social factors. Despite their different views of the pathophysiology of fibromyalgia, Drs. Wolfe and Clauw agree that fibromyalgia symptoms are real and should be addressed.