Fibromyalgia: New Criteria Improve Diagnosis

Diedtra Henderson

February 13, 2014

The 2011 modification of the American College of Rheumatology's (ACR's) 2010 preliminary criteria for diagnosing fibromyalgia (2011ModCr) reliably diagnoses the disorder in a large, diverse group of patients suffering from pain. In addition, easier-to-use alternate criteria with broader symptoms and pain locations are even more specific, according to the cross-sectional survey.

Robert M. Bennett, MD, from the Oregon Health & Science University in Portland, and colleagues published their results online February 4 in Arthritis Care & Research.

According to the National Institutes of Health, fibromyalgia affects 5 million American adults, with women accounting for 80% to 90% of diagnosed cases. The disorder is characterized by muscle pain and fatigue and is marked by "tender points," specific locations throughout the body that hurt when pressure is applied.

The 2011ModCr include 19 pain locations and 6 self-reported symptoms: difficulty sleeping, fatigue, poor cognition, headaches, depression, and abdominal pain. The research team, geographically diverse clinical investigators skilled in diagnosing and managing patients with fibromyalgia, sought to validate the modified criteria in a more diverse set of patients with chronic pain, typical of the patients clinicians see daily.

From July 2012 to March 2013, the authors recruited 321 patients from the practices of 5 rheumatologists, 2 pain specialists, and 1 psychologist in 4 states. Patients completed 5 questionnaires that included a previously-validated 10-item symptom impact questionnaire, as well as a rating of their pain and tenderness in 28 locations on a 0 to 10 severity scale The researchers analyzed the patient's experience using an alternate diagnostic criterion that leveraged the 28-item pain location inventory and the symptom impact questionnaire.

The 2011ModCr provided a sensitivity of 83.5% and specificity of 67.2% and correctly classified 73.8% of patients. The alternate criteria (2013 AltCr) were slightly less sensitive, at 80.7%, but had higher specificity (79.6%) and classified 80.1% of patients correctly.

"A notable finding was a 31% prevalence of males in the 2011ModCr [false-positives (FPs)], and a 34% prevalence of males in the 2013AltCr FPs; thus the overall male prevalence (i.e. [true-positive] + FP) was 16% for the 2011ModCr and 14% for the 2013AltCr, compared with 6% ACR 1990," the authors write.

With the ACR 1990 criteria, once considered the gold standard, it was difficult to accurately diagnose patients.

"Women are more tender than men; men often don't get diagnosed," Dr. Bennett told Medscape Medical News. Even for women, 1 clinician could identify a sufficient number of tender points to make a diagnosis 1 day, and then the next clinician the patient visited could fail to do so. "[The patient] goes from having fibromyalgia to not having fibromyalgia," he said. "These new criteria are easier to use."

"The 2011ModCr embrace a wider spectrum of patients with [fibromyalgia]-like symptoms than the ACR 1990," the authors report.

Although Jan Favero Chambers, president and founder of the National Fibromyalgia & Chronic Pain Association, Logan, Utah, is grateful for "the clarity this criteria brings" to fibromyalgia diagnosis, she tells Medscape Medical News that the existence of 5 different diagnostic criteria may sow confusion.

Rheumatologists are comfortable applying the diagnostic criteria, but the diagnostic skills of generalists vary. As it stands now, she says, people trying to learn what is going wrong with their bodies visit between 3 and 5 clinicians and spend thousands of dollars before being diagnosed with fibromyalgia.

The study authors note that independent assessment of the 2013AltCr will be needed in a larger, more diverse set of patients with chronic symptoms.

"[W]e have provided independent validation of the 2011ModCr in a patient sample composed of a wider range of chronic pain disorders than reported in previous studies," the authors conclude. "We have also explored alternative criteria (2013AltCr) based on the [system impact questionnaire] symptom scale and number of pain locations. These alternative criteria are comparable to the 2011ModCr in diagnostic sensitivity and somewhat better in specificity; importantly they have the advantage of using just one combination of pain locations and symptoms, and one time interval for reporting symptoms."

Financial support for this study was provided by the Fibromyalgia Information Foundation.

Arthritis Care Res. Published online February 4, 2014. Abstract

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