A series of statistical analyses of data from 581 patients with fibromyalgia suggests that they can be placed into one of four groups according to the severity of core symptom domains.

The patients completed a comprehensive symptom profile guided by recommendations from the Outcome Measures in Rheumatology (OMERACT) fibromyalgia working group. They were categorized by the investigators as having low symptom intensity, moderate symptoms with relatively little negative mood, moderate symptoms with more negative mood or high symptom intensity.

“We’re highlighting that you can’t assume every patient with fibromyalgia is exactly the same,” explained lead investigator Ann Vincent, MD, associate professor of medicine, Mayo Clinic, Rochester, Minn., after she and her colleagues presented a poster on the findings at the American Academy of Pain Medicine’s 2014 annual meeting (poster 131). “We, as clinicians, need to assess the overall symptom burden and severity of individual symptoms to guide our treatments and management recommendations. For example, patients with high symptom severity may be best served by intensive pain rehabilitation in contrast to a patient with low symptom severity, for whom a combination of medications and physical and cognitive therapy may be sufficient.”

She said further research is needed to determine whether different strategies for different symptom-severity groups are indeed effective.

Another expert in the field, who was not involved in the study, said he was impressed by the research.

“To my knowledge, this is the largest study of its kind in patients with fibromyalgia and the first to use the OMERACT recommendations,” said Chad Boomershine, MD, PhD, assistant professor at Vanderbilt University, Nashville, and a rheumatologist in private practice in Franklin, both in Tennessee, who specializes in treating fibromyalgia. “The importance of the authors’ findings that individual fibromyalgia patients differ from one another in the severity of various symptoms cannot be overstated. Assessing the severity of all OMERACT symptoms and using this evaluation to develop an individualized treatment plan is essential for effective fibromyalgia management.”

The idea of defining subgroups within fibromyalgia is not new, because fibromyalgia is a very heterogeneous disorder, noted Dr. Vincent. What is new is creating subgroups based on the framework developed by the OMERACT fibromyalgia working group. The core symptom domains that she and her colleagues focused on were pain, multidimensional functioning, fatigue, sleep disturbance, tenderness, dyscognition, stiffness, depression and anxiety. Their work was supported partly by the Center for Clinical and Translational Science at Mayo Clinic.

Dr. Vincent’s team used validated self-report questionnaires to measure the severity of each of these core symptom domains in randomly selected patients from the Mayo Fibromyalgia Registry. The patients’ median age was 55.6 years and their median body mass index was 29.2 kg/m2.

The researchers analyzed the resulting data using hierarchical agglomerative clustering, a technique that identifies the largest clusters within data sets—in this case, groups of patients with similar symptom characteristics based on the assessment tools.

The investigators found four main clusters of patients: Cluster 1 had low intensity of all of the symptoms; Cluster 4 had higher intensity of the symptoms; and Clusters 2 and 3 had moderate levels of all of the symptoms. The two intermediate groups could be most clearly differentiated based on their levels of anxiety and depression, with Cluster 2 patients having significantly less anxiety and depression than Cluster 3 patients.

The investigators validated their results by using the Revised Fibromyalgia Impact Questionnaire (FIQ-R) score as an external benchmark. Cluster 1 had the lowest mean FIQ-R total score whereas Cluster 4 had the highest, and Clusters 2 and 3 fell between the two extremes.

“It remains to be seen whether these findings will help us develop a better understanding of what this condition is from a biological viewpoint, and how treatment can be better targeted to its root cause or causes,” said Charles E. Argoff, MD, professor of neurology, Albany Medical College, and director, Comprehensive Pain Center, Albany Medical Center, both in Albany, N.Y., and a Pain Medicine News editorial board member, who was not involved in the study. “In addition, this work may lead to an appreciation that fibromyalgia is simply not a single condition but a spectrum of disorders, and thus personalized assessment and treatment is key to its successful management.”

—Rosemary Frei, MSc



Dr. Boomershine serves on the speakers bureau and as an advisor for Pfizer Inc. Drs. Argoff and Vincent reported no relevant financial conflicts of interest.