Tampa, FL—Researchers have detected 2 different subclusters of patients with fibromyalgia, according to results presented at the American Pain Society's 2014 Annual Meeting. One group has widespread pain as one of their predominant characteristics and the other subcluster—which is far less common than the first—comprises patients with fatigue as their primary concern (Lukkahatai N, et al. Tampa, FL: American Pain Society; 2014. Abstract 157).
Furthermore, patients with fatigue as their primary concern had a stronger relationship between pain intensity and pain interference, as well as between symptom-severity score and mental fatigue compared with patients in the other subcluster.
The investigators believe that these findings underline the complexity of fibromyalgia and also point to possible individualization of treatment in the future. “It’s a human experience—it’s not like cancer where you can see the tumor and can treat it right away,” first author Nada Lukkahatai, RN, PhD, told Value-Based Care in Rheumatology. “How are you going to manage the patients who come to you and one day they say ‘the pain is here’ and the next day they say ‘the pain is there and the medication you gave them doesn’t work’? To better manage these patients we try to look for a pattern and then eventually this will enable clinicians to individualize treatment accordingly.”
Dr Lukkahatai was a postdoctoral fellow at the National Institute of Nursing Research, National Institutes of Health, Bethesda, Maryland, during this study. Now she is an assistant professor in the Physiological Nursing Department at the University of Nevada, Las Vegas. The team analyzed the initial-visit self-reported questionnaire responses of 120 patients diagnosed with fibromyalgia using the 1990 or 2010 American College of Rheumatology criteria. The study was part of a prospective, longitudinal, observational study from a MedStar Health Research Institute protocol at Georgetown University.
Ninety percent of the patients were women and their mean age was 46.3 years. Just under one-third were African American and approximately two-thirds were white non-Hispanic. They had a mean of 14.28 tender joints.
The study consisted of the construction of a model in which the researchers mapped out the relationships of widespread pain and symptom severity, with pain, cognitive function, daytime sleepiness, fatigue, and psychological status. They also determined the strength of these relationships.
The researchers demonstrated 2 distinct subclusters based on fibromyalgia syndrome diagnostic tools, Widespread Pain Index and Symptom Severity Score. One comprised 94 (78%) patients in whom widespread pain predominated, along with unrefreshed waking and somatic symptoms. In the other group, which consisted of 26 patients, fatigue and cognitive dysfunction were particularly strong. Overall, the symptoms of patients in the first subcluster were more intense than in the second.
The investigators also detected differences between the 2 groups in the strength of associations between different categories of symptoms. For example, the relationship between pain intensity and pain interference was stronger in the fatigue subcluster than in the widespread-pain subcluster, while the association between catastrophizing and total fatigue was stronger in the widespread-pain subcluster.
“We intend to do a longitudinal study with a larger number of patients to see if the groupings remain the same or change over time and whether we can implement any interventions targeted at each of these subclusters,” said Dr Lukkahatai.