New Symptom-based Criteria Accurately Identify Fibromyalgia

By eliminating need for physical exam in diagnosis of fibromyalgia, new criteria enable co-morbidity studies in patients with IBS.

The authors of “Validation of a New Symptom-based Fibromyalgia Criteria for Irritable Bowel Syndrome Comorbidity Studies,” published in the January 2011 issue of Journal of Neurogastroenterology and Motility, sought to determine the validity of a symptom-based fibromyalgia diagnostic criteria that includes a regional pain scale and a visual analogue scale for fatigue.

Although irritable bowel syndrome (IBS) and fibromyalgia syndrome “are common functional disorders that share many characteristics,” with fibromyalgia prevalence in patients with IBS ranging from 30-70% and patients diagnosed with both disorders often having “more severe IBS symptoms, more psychopathology, lower health-related quality of life and a lower score on the sense of coherence questionnaire for coping skills than patients with only one of these disorders,” the authors noted that co-morbidity studies between fibromyalgia and IBS are difficult to conduct, in large part because the diagnosis of IBS is symptom-based, whereas the diagnosis of fibromyalgia requires a physical exam.

Because such co-morbidity studies could potentially “advance our understanding of these associations in terms of pathogenesis, the impact on symptom severity, health-related quality of life and patient care,” the authors studied the use of a fibromyalgia diagnostic criteria developed by Wolfe and Michaud that does not require a physical exam. The criteria, a “composite score of their regional pain scale (RPS) and a visual analog scale (VAS) for chronic fatigue,” has been shown in studies to have a 73% concordance rate with the American College of Rheumatology (ACR) fibromyalgia diagnostic criteria.

Accordingly, the researchers tested the Wolfe-Michaud criteria “in a population of IBS and FMS patients, as well as healthy controls, using the ACR criteria as the gold standard.” For the study, they recruited an age-matched cohort of 30 women who had been diagnosed with fibromyalgia, 27 with IBS, and 28 controls. The RPS included in the Wolfe-Michaud criteria asks respondents to rate the level of pain or tenderness they felt in 19 body areas over the previous seven days as "none," "mild," "moderate" or "severe." Any response other than “none” is rated as “positive,” giving a possible RPS score range of 0-19 The VAS asks patients to rate the degree of fatigue they felt over the previous week on a scale from 0-10. A fibromyalgia diagnosis requires a composite RPS score of 8 or higher and a VAS score of 6 or higher. Patients were diagnosed with IBS using the Rome II criteria.

In addition to examination with the Wolfe-Michaud RPS and VAS, patients also underwent a physical exam to determine the number of ACR-defined tender points and were examined via dolorimeter for “threshold of tenderness at tender points.”

The authors reported that the sensitivity and specificity of the new composite diagnostic score for fibromyalgia (RPS 8 or higher, VAS 6 or higher) were “82.9% and 96.0%, respectively and the positive and negative predictive values were 93.5% and 88.9%, respectively.” The “best test characteristics” were found when the composite score for fibromyalgia was defined as RPS 11 or higher and VAS 5 or higher. IN that case, “sensitivity and specificity were 88.6% and 98.0%, respectively, for the entire study population. The positive and negative predictive values were 96.9% and 92.5%, respectively.”

In the IBS group, the positive predictive value of the new composite score for fibromyalgia “was 100.0%, negative predictive factor 91.7% with relatively low sensitivity.”

In their discussion of these results, the authors wrote that their study demonstrates that the RPS “can be used as a valid substitute for the ACR criteria when large study groups make the physical examination unpractical or for epidemiological surveys that are conducted in large populations by mail, telephone or other indirect means.” The sensitivity and specificity of the criteria calculated in this study means that “studies of co-morbidity using these criteria could present a slight underestimate of the actual co-morbidity rates.” The sensitivity and specificity of the revised criteria (RPS 11 or higher and VAS 5 or higher) were “of particular interest in that the number of painful regions by RPS (≥ 11) corresponds with the minimum number of tender points required by the ACR at physical examination (≥ 11).”

The authors concluded that these results demonstrate that “the new criteria can be used in large-scale general population-based studies and not only on studies of patient populations with IBS and other functional disorders.” This would broaden our understanding “on the pathogenesis of co-morbid conditions and the implications for patients in terms of impact on symptom severity and health-related quality of life as well as potentially leading to improved patient care.”

HCPLive wants to know:

Based on these results, would you consider using these diagnostic criteria when evaluating patients for fibromyalgia?

In your experience, how much overlap is there between patients with irritable bowel syndrome and fibromyalgia? Do patients with both disorders tend to have more severe IBS symptoms?

The authors of this study note that some experts have proposed that IBS and fibromyalgia “share a common pathogenesis or even represent a single entity that has been split into separate diagnoses because of the hyper-specialization of the medical profession.” Do you agree with this assessment?

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