Diagnosing Fibromyalgia as a Disease, an Illness, a State, or a Trait?

In this issue of Arthritis Care & Research, Wolfe and colleagues report that there were considerable disparities between rheumatologists’ clinical diagnosis of fibromyalgia and a criteriabased diagnosis; in their study, Wolfe et al used a modification of the 2010 American College of Rheumatology (ACR) preliminary diagnostic criteria (1). Is this surprising? Based on their findings, do we need to further modify the fibromyalgia classification criteria or better educate our rheumatology trainees and staff? How do we apply diagnostic criteria to clinical practice? Since fibromyalgia became the generally accepted label for chronic, widespread musculoskeletal pain in 1981, rheumatologists have often expressed doubt regarding its pathophysiology, diagnostic utility, and therapy. In order to provide diagnostic clarity and consensus, the ACR endorsed initial criteria for the classification of fibromyalgia in 1990 (2). After 20 years of utilization of these 1990 criteria in rheumatology practice and research, the criteria were modified in 2010 (3) and again in 2011 (4). It is therefore timely to review the evolution of these sets of fibromyalgia criteria. Classification criteria for the diagnosis of fibromyalgia, as well as for common illnesses such as depression, tensiontype headaches, and irritable bowel syndrome, are established by a panel of experts, then fieldtested in previously diagnosed patients and in healthy controls or in patients with illnesses that have similar characteristics. Until biomarkers or genetic testing provides more objective disease markers, these common conditions will continue to be symptombased diagnoses. As such, they are often considered to be “soft” diagnoses. Our panel of experts recommended various signs and symptoms for the 1990 fibromyalgia criteria, which were then tested in 300 patients with a previous diagnosis of fibromyalgia and in control patients with rheumatic disorders that could be confused with fibromyalgia (2). The combination of widespread pain and mild or greater tenderness in ≥11 of 18 tender point sites provided good sensitivity and specificity and were selected by consensus as the 1990 classification criteria. Implied, although not formally part of the criteria, fibromyalgia was to be considered only in individuals whose symptoms could not be explained by another rheumatic or medical disorder. It was reassuring that fibromyalgia did not differ in those patients with a concurrent rheumatic disease, such as rheumatoid arthritis (RA), thereby abandoning the term secondary fibromyalgia. After 20 years of use of these criteria in clinical practice and research, the fibromyalgia criteria were modified in 2010 (3). It was apparent that the tender point examination was difficult to stan dardize and not widely practiced, especially in primary care. The focus on specific tender point locations implied peripheral tissue pathology, whereas it had become clear that fibromyalgia was a manifestation of central pain sensitization. These 2010 criteria emphasize symptoms, such as fatigue and sleep disturbances, and measure symptom severity over time, recognizing the changing nature of those symptoms. These 2010 criteria were slightly modified in 2011, eliminating the physician’s estimate of the extent of somatic symptoms and substituting patient selfreported symptoms, thereby eliminating the need for physician involvement in diagnosis (4). The socalled “gold standard” in each of these criteria sets, as well as those used for depression, headaches, and other common illness, is expert opinion. In evaluating the sensitivity and specificity of the 2010 criteria, the gold standard was the 1990 criteria. It was explicitly stated that these 2010 cri teria were “not meant to replace the ACR classification criteria” (3). We also stated that the 2011 criteria modification were for epidemiologic and clinical studies and “not to be used for selfdiagnosis” (4). However, Wolfe and colleagues chose these 2011 selfreport fibromyalgia criteria as their gold standard for a fibromyalgia diagnosis, despite voicing concern regarding the “selfreport nature of fibromyalgia” (1). Their finding of a significant discrepancy between these 2011 criteriabased diagnoses and a physicianbased diagnosis of fibromyalgia should not be surprising. Jones et al reported that the prevalence of fibromyalgia was significantly higher when using these 2011 criteria compared to the 1990 or 2010 criteria (5). Vincent and colleagues found that 1% of the gen-