Clinical Context

Fibromyalgia is characterized by a complex spectrum of symptoms and findings that can make the diagnosis challenging, and the authors of the current study provide a review of different diagnostic criteria for fibromyalgia. They note that the widely used 1990 American College of Rheumatology (ACR) criteria focus singularly on pain vs other aspects of fibromyalgia, and practicing physicians rarely evaluate the possible 18 tender points at the heart of these criteria.

New modified criteria for the diagnosis of fibromyalgia proposed by the ACR in 2011 (2011ModCr) included 19 objective pain locations plus a subjective patient assessment of 6 symptoms, including impaired sleep, fatigue, poor cognition, headaches, depression, and abdominal pain. Previous research has found that these criteria demonstrate good reliability in discriminating patients with fibromyalgia, with specificity greater than sensitivity. The current study by Bennett and colleagues further examines the reliability of the 2011ModCr and evaluates novel diagnostic criteria for fibromyalgia.

Study Synopsis and Perspective

The 2011 modification of the ACR's 2010 preliminary criteria for diagnosing fibromyalgia (2011ModCr) reliably diagnoses the disorder in a large, diverse group of patients experiencing 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 adults in the United States, 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 treating 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 severity scale of 0 to 10. 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 a 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. In addition, 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

Clinical Implications

• The ACR 1990 criteria focus singularly on pain vs other aspects of fibromyalgia. However, the 2011ModCr included 19 objective pain locations plus a subjective patient assessment of 6 symptoms, including impaired sleep, fatigue, poor cognition, headaches, depression, and abdominal pain. Previous research has found these criteria to have good reliability in discriminating patients with fibromyalgia, with specificity greater than sensitivity.
• The current study by Bennett and colleagues finds that both the 2011 ModCr and novel instrument had strong operating characteristics in the diagnosis of fibromyalgia. The novel instrument improved on the specificity of the 2011ModCr, and the number of pain sites was the most important element in identifying fibromyalgia with either the novel instrument or the 2011ModCr.

CME Test