Reliability, Factor Structure and Predictive Validity of the Widespread Pain Index and Symptom Severity Scales of the 2010 American College of Rheumatology Criteria of Fibromyalgia

Abstract

Fibromyalgia syndrome (FMS) is a chronic condition of widespread pain. In 2010, the American College of Rheumatology (ACR) proposed new diagnostic criteria for FMS based on two scales: the Widespread Pain Index (WPI) and Symptoms Severity (SS) scale. This study evaluated the reliability, factor structure and predictive validity of WPI and SS. In total, 102 women with FMS and 68 women with rheumatoid arthritis (RA) completed the WPI, SS, McGill Pain Questionnaire, Trait Anxiety Inventory, Fatigue Severity Scale, Oviedo Quality of Sleep Questionnaire, and Beck Depression Inventory. Pain threshold and tolerance and a measure of central sensitization to pain were obtained by pressure algometry. Values on WPI and SS showed negative-skewed frequency distributions in FMS patients, with most of the observations concentrated at the upper end of the scale. Factor analysis did not reveal single-factor models for either scale; instead, the WPI was composed of nine pain-localization factors and the SS of four factors. The Cronbach’s α (i.e., Internal consistency) was 0.34 for the WPI,0.83 for the SS and 0.82 for the combination of WPI and SS. Scores on both scales correlated positively with measures of clinical pain, fatigue, insomnia, depression, and anxiety but were unrelated to pain threshold and tolerance or central pain sensitization. The 2010 ACR criteria showed 100% sensitivity and 81% specificity in the discrimination between FMS and RA patients, where discrimination was better for WPI than SS. In conclusion, despite their limited reliability, both scales allow for highly accurate identification and differentiation of FMS patients. The inclusion of more painful areas in the WPI and of additional symptoms in the SS may reduce ceiling effects and improve the discrimination between patients differing in disease severity. In addition, the use of higher cut-off values on both scales may increase the diagnostic specificity in Spanish samples.

Beyond bones: The relevance of variants of connective tissue (hypermobility) to fibromyalgia, ME/CFS and controversies surrounding diagnostic classification: an observational study

“…28 In particular, ACR widespread pain index and ACR symptom severity scale allow for highly accurate identification and differentiation of fibromyalgia patients. 29 Our findings of high rates of generalised joint laxity in this population are in line with other studies of ME/CFS, however, ours is the first to directly compare diagnostic assessments for hypermobility. 13 Fibromyalgia and ME/CFS are both associated Beyond bones with inflammatory abnormalities and dysautonomia (eg orthostatic intolerance, postural orthostatic tachycardia syndrome and orthostatic hypotension), which is also commonly observed in symptomatic hypermobility.…”

Diagnostic Criteria for Fibromyalgia: Critical Review and Future Perspectives

“…The 1990 criteria have been considered as stricter than the 2010 criteria, such that only more severely affected patients are identified [2]. Studies recruiting FMS patients according to the 1990 ACR criteria reported higher mean WPI and SS scores than studies in which patients were recruited using the 2010 ACR criteria [2,72]. Nevertheless, a study which divided FMS patients into adapted (i.e., lower levels of psychological distress, catastrophizing, and fatigue) and maladapted profile (including problems in resilience, catastrophizing, and memory) found in the adapted profile subgroup a greater percentage of patients fulfilling the 1990 ACR criteria but not the 2011 criteria, whereas the opposite occurs in the maladapted profile subgroup.…”

Flotation Restricted Environmental Stimulation Therapy for Chronic Pain

“…Pain area and WPI were derived from electronic pain drawings acquired with the SymptomMapper application. 38 The WPI has been used for the diagnosis of fibromyalgia 34 , 39 and has been associated with central sensitization. 40 …”