Progression of fibromyalgia: results from a 2-year observational fibromyalgia and chronic pain study in the US

BACKGROUND A previous fibromyalgia (FM) research reports that 20%-47% of diagnosed patients may not meet the study definition of FM 1-2 years after diagnosis. The aim of this study was to gain a better understanding of the progression of FM in a geographically diverse cohort over a 2-year time period. METHODS This cohort study followed 226 subjects recruited online to assess FM and chronic widespread pain (CWP) diagnosis stability over time. At enrollment (baseline), subjects provided informed consent, completed an online questionnaire consisting of the London Fibromyalgia Epidemiology Study Screening Questionnaire to screen for CWP (bilateral pain above/below waist lasting ≥1 week in the past 3 months), visited a site for physician evaluation for FM, and completed a questionnaire with validated patient-reported outcome instruments. Subjects were classified into mutually exclusive groups: FM+CWP+ (screened positive for CWP and received physician diagnosis of FM), FM-CWP+ (screened positive for CWP but did not receive physician diagnosis of FM), and FM-CWP- (screened negative for CWP). Approximately 2 years later (follow-up), subjects were reassessed at the same study site and completed a questionnaire with the same patient-reported outcomes. RESULTS Seventy-six FM+CWP+ subjects completed assessments at both time points; 56 (73.7%) met the FM study definition at follow-up. Twenty subjects no longer met the FM study definition (eleven became FM-CWP- and nine became FM-CWP+). Ten subjects (two from FM-CWP- and eight from FM-CWP+) transitioned into the FM+CWP+ group at follow-up; they reported more tender points and pain interference with sleep and worse physical function at baseline compared with subjects who did not transition to FM+CWP+. Most (76.7%) of the subjects who transitioned into/out of FM+CWP+ experienced changes in CWP, number of positive tender points, or both. CONCLUSION The results suggest that some FM+CWP+ patients experience fluctuation in symptoms over time, which may reflect the waxing and waning nature of FM and affect diagnosis and treatment.