Using Different Fibromyalgia Criteria Affects Prevalence Estimates

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A recent paper illustrates how using different fibromyalgia criteria affects reports of its prevalence.¹

Writing in Arthritis Care & Research, researchers found the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks–American Pain Society Pain Taxonomy (AAPT) criteria caused far more people to be categorized as having fibromyalgia than criteria put forth by the 2016 revisions to the 2010/2011 fibromyalgia diagnostic criteria in a randomly selected German population to whom researchers applied both sets of criteria.^1-3 Using the AAPT criteria, Häuser et al. found the prevalence of fibromyalgia was 73% greater than with the modified 2016 criteria. Individuals diagnosed according to the AAPT criteria also had fewer pain sites and less severe symptoms, the researchers say.¹

“The criteria overlap, but they don’t agree well,” says senior author Frederick Wolfe, MD, director of the National Databank for Rheumatic Diseases, Wichita, Kan. “The two sets of criteria identified two sets of patients. The criteria do not solve the question of who has fibromyalgia.”

Dr. Wolfe, who was named an ACR Master in 2001, led the development of the 1990 and 2010 ACR fibromyalgia criteria, and subsequent modifications.

A Short History

Criteria for fibromyalgia have changed over the years. The 1990 ACR classification criteria required the presence of widespread pain and specialized physical examinations to quantify tender points. Not many providers had training to perform the exams.

The subsequent 2010 ACR diagnostic criteria allowed providers to base a diagnosis of fibromyalgia on the patient’s history. The 2010 diagnostic criteria required assessment of the extent of fatigue, unrefreshed sleep and cognitive dysfunction or remembering, along with the somatic symptom burden. The 2010 ACR criteria involved asking patients about pain or tenderness in 19 body regions, with a resultant score on a widespread pain index (WPI). Physicians also asked patients about fatigue, cognitive function, poor sleep, and a wide array of other symptoms for scoring on a symptom severity scale (SSS).

Dr. Wolfe

A diagnosis of fibromyalgia under the 2010 criteria required the patient: 1) have a WPI score of 7 or higher and an SSS score of 5 or higher, or a WPI score of 3–6 and an SSS score of 9 or higher; 2) experience symptoms at a similar level for at least three months; and 3) have no other disorder that would otherwise fully explain their pain.⁴

A 2011 update to the 2010 ACR criteria replaced the long list of elements a clinician had to assess with a questionnaire asking patients about depression, irritable bowel syndrome symptoms and headache. Adding scores from the WPI and SSS yielded an index of 0–31, called the polysymptomatic distress scale (PDS).⁴ The PDS is a measure of overall symptom severity, Dr. Wolfe explains.

The scale’s name is controversial. Some physicians—including Daniel Clauw, MD, professor of anesthesiology, rheumatology and psychiatry at the University of Michigan Medical School, Ann Arbor, and the author of an editorial published alongside the Häuser et al. study—maintain the PDS does not measure patient distress.

The 2016 modification of the 2010/2011 criteria does not exclude the presence of other pain conditions.

The modification raised the WPI minimum score from 3 to 4 and added a requirement that the pain be generalized.³ The 2016 modification retains the SSS from the earlier version of the criteria, adding it to the WPI to form what is now called the fibromyalgia severity scale or polysymptomatic distress scale (FSS/PDS). The FSS/PDS can be used as a continuous scale or for diagnostic purposes using the specified thresholds.

AAPT criteria were issued as a diagnostic system intended to be clinically useful and consistent across various chronic pain disorders—including fibromyalgia. The system includes not only core or required dimensions that can be used for diagnosis, but also supportive signs and symptoms that can help clinicians increase their confidence in the diagnosis.

The AAPT diagnostic cutoff for fibromyalgia is based on the presence of pain in at least six of nine pain sites and moderate to severe sleep problems or fatigue for at least three months. AAPT pain regions include the head, chest and abdomen, which are not scored in the 2016 modification.^2,5

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.

Clinician Takeaway

For practicing clinicians, the paper’s main value is how it highlights the differences between the two instruments for diagnosing fibromyalgia, says Leslie J. Crofford, MD, an AAPT co-author and chief of the Division of Rheumatology and Immunology, Vanderbilt University Medical Center, Nashville, Tenn.

The AAPT criteria set a lower bar for identifying fibromyalgia. That’s by design, she says, noting the goal of the criteria was to help clinicians—especially primary care providers—identify and effectively treat symptoms early. AAPT criteria were not developed to ascertain population prevalence, Dr. Crofford notes.

Primary care physicians commonly lack confidence when diagnosing fibromyalgia and other pain disorders, says Dr. Crofford. “For that reason,” she says, “rheumatologists get lots of referrals not only for fibromyalgia, but also for rheumatoid arthritis and osteoarthrosis and other pain conditions in the AAPT framework.”

The AAPT framework encompasses a wide array of pain disorders and can help primary care providers decide which disorder most likely causes a patient’s pain and start treatment earlier.

A distinct advantage of the 2016 modified criteria, according to Dr. Crofford, is the inclusion of a severity scale “so you can follow patients over time and see if they get better or worse.”

Dr. Crofford

Dr. Crofford stresses the importance of early identification and treatment of core fibro­myalgia symptoms, such as sleep disorders. She urges clinicians to avoid situations in which patients who are suffering get frustrated and feel like clinicians are not listening to them. That’s when they may develop an “oppositional relationship with the healthcare system,” she says.

“The clinician’s role is to carefully listen to the patient, to evaluate their complaints, put them in an understandable framework for patients, and to work with them to address symptoms to the best of your ability,” Dr. Crofford says. “Make sure you work with patients to improve their overall symptoms and function.”

Deborah Levenson is a writer and editor based in College Park, Md.

References

1. Häuser W, Brähler E, Ablin J, Wolfe F. Modified 2016 American College of Rheumatology fibromyalgia criteria, the analgesic, anesthetic, and addiction clinical trial translations innovations opportunities and networks–American Pain Society pain taxonomy, and the prevalence of fibromyalgia. Arthritis Care Res (Hoboken). 2021 May;73(5):617–625.
2. Arnold LM, Bennett RM, Crofford LJ, et al. AAPT diagnostic criteria for fibromyalgia. J Pain. 2019 Jun;20(6):611–628.
3. Wolfe F, Clauw DJ, FitzCharles M, et al. 2016 revisions to the 2010/2011 fibromyalgia diagnostic criteria [abstract]. Arthritis Rheumatol. 2016;68(suppl 10).
4. Boomershine CS. Fibromyalgia clinical presentation. Medscape. 2020 Apr 23.
5. Clauw DJ. Time to stop the fibromyalgia criteria wars and refocus on identifying and treating individuals with this type of pain earlier in their illness. Arthritis Care Res (Hoboken). 2021 May;73(5):613–616.