Mayo Clinic Fibromyalgia Researchers Propose Four-Cluster Symptom Profiling Model

Mayo Clinic Fibromyalgia Researchers Propose Four-Cluster Symptom Profiling Model

A problem for clinicians treating patients with fibromyalgia syndrome (FM) is that they often are not equipped with effective methods to assess fatigue, and without dependable ways to measure fatigue, it’s difficult to evaluate treatment efficacy.

However, according to a research article published in the journal Arthritis Research & Therapy, persons with Fibromyalgia syndrome can be categorized in four clusters respectively sharing similar symptom profiles, using the Outcome Measures in Rheumatology (OMERACT) core symptom domains.

The Open Access paper, entitled: OMERACT-based fibromyalgia symptom subgroups: an exploratory cluster analysis is coauthored by corresponding author Ann Vincent and Mary O. Whipple of the Division of General Internal Medicine at the Mayo Clinic in Rochester, Minnesota; Tanya L. Hoskin of the Mayo Clinic Division of Biomedical Statistics and Informatics; Daniel J. Clauw and David A. Williams of the University of Michigan’s Health System Chronic Pain and Fatigue Research Center in Ann Arbor; Debra L. Barton of the Mayo Clinic Division of Medical Oncology; and Roberto P. Benzo of the Mayo Clinic Division of Pulmonary and Critical Care Medicine.

annvincentA particular research interest of Dr. Ann Vincent, M.B.B.S., M.D.,, a junior investigator and consultant in the Mayo Clinic’s Division of General Internal Medicine in Rochester, Minnesota, and medical director of the Fibromyalgia and Chronic Fatigue Clinic, is fatigue as it relates to fibromyalgia, which is estimated to afflict from three to six million people in the United States alone, with fatigue cited as a symptom by about three-quarters of FM patients, and on finding better ways to evaluate and treat fatigue in fibromyalgia.

“Not much is known about fatigue related to fibromyalgia,” Dr. Vincent notes in a Mayo Clinic profile. “Many know that pain is a symptom of fibromyalgia, but fatigue is a serious issue too,” observing that clinicians treating FM often don’t have very effective methods with which to assess fatigue, and that without dependable ways to measure fatigue, it’s difficult to evaluate treatment efficacy. Dr. Vincent suggests that combining a range of evaluative techniques, such as self-report questionnaires and physiological measurements, will lead to better characterization of FM-related fatigue. After determining new ways to assess fibromyalgia-related fatigue, with her research objective the design of clinical trials to evaluate novel fatigue treatments.

Dr. Vincent’s topics of investigation include comorbid conditions common in fibromyalgia patients, such as obesity, diabetes, hypertension, rheumatologic conditions, sleep disorders, depression and anxiety, and also include evaluating the roles that physical activity, emotional well-being, mind-body practices, natural products, and other complementary health approaches like mind-body practices play in mitigating FM symptoms and improving quality of life of patients.”My patients inspire my research questions, and they ultimately benefit from what I learn through my research,” Dr. Vincent observes.

The particular aim of the Arthritis Research & Therapy study was to identify subsets of patients with fibromyalgia who share similar symptom profiles using Outcome Measures in Rheumatology (OMERACT) core symptom domains.

OMERACT is an independent initiative of international health professionals interested in rheumatology outcome measures, which over the past 20 years, has played a critical role in the development and validation of clinical and radiographic outcome measures in rheumatoid arthritis, osteoarthritis, psoriatic arthritis, fibromyalgia, and other rheumatic diseases.

Photo caption: Participants at the first OMERACT Conference on Outcome Measures in Rheumatoid Arthritis 29 April – 3 May 1992 at Maastricht, The Netherlands – Image Courtesy OMERACT


The organization notes that agreement regarding use of standardized endpoints in randomized controlled trials and longitudinal observational studies is extremely important, use of which facilitates outcome comparisons across studies in aid of providing the best estimates of benefit and safety of therapeutic interventions across differing patient populations. A scholarly profile of OMERACT can be found here:

The scientists in Dr. Vincent’s team note that despite chronic, widespread musculoskeletal pain affecting ligaments, tendons, and muscles throughout the body being fibromyalgia’s main symptom, the disorder actually presents as a heterogeneous symptom complex that remains poorly understood. They observe that In addition to pain, frequently occurring symptoms associated with FM include fatigue, unrefreshing sleep, cognitive difficulties, headache, anxiety and depression, and that patients with FM frequently present with these symptoms in varying combinations and degrees of severity, further complicating clinicians’ ability to understand FM, and making study of the disorder challenging. Their research premise was to investigate if stratifying patients into more homogeneous subgroups could facilitate better understanding of FM.

A total of 581 females with a mean age of 55.1 years participated as subjects, and it was determined that a four-cluster model best fit the data. The four clusters respectively divided the sample into severity levels.

Cluster 1 reflects the lowest average levels across all symptoms, and cluster 4 the highest. Clusters 2 and 3 contain more moderate symptom levels, differing mainly in anxiety and depression profiles — Cluster 2 having lower levels of depression and anxiety than Cluster 3, despite higher levels of pain. They say results of the cluster analysis of the external sample looked very similar to those found in the original cluster analysis, save for a slight difference in sleep problems, notwithstanding that some patients in the validation sample who were significantly younger and had more severe symptoms.

The researchers applied core OMERACT symptom domains, which allowed for clustering based on comprehensive symptom profiling. They conclude that although their exploratory cluster solution needs confirmation in a longitudinal study, it also distinguishes itself by being the first study of its kind to incorporate a comprehensive symptom spectrum as recommended by the OMERACT FM working group, and that this approach could provide a model to support study of individualized clinical evaluation, and corroborates previous cluster reports. They acknowledge that this cluster solution needs longitudinal study and that feasibility and outcomes of this approach must be further assessed before conclusions as to its clinical implications can be made but that this study is a first step toward that objective.

Arthritis Research & Therapy
Outcome Measures in Rheumatology (OMERACT)
Mayo Clinic

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Mayo Clinic
Outcome Measures in Rheumatology (OMERACT)