Evaluating soreness symptoms of fibromyalgia: Establishment and validation of the Revised Fibromyalgia Impact Questionnaire with Integration of Soreness Assessment.

Background: Fibromyalgia is a chronic disorder characterized by widespread musculoskeletal pain. A common complaint is soreness. However, until now, no assessment tool is available to address soreness and evaluate its impact on disease severity. We aimed to establish a questionnaire for soreness assessment and to evaluate its validity in fibromyalgia patients.

Methods: Patients diagnosed with fibromyalgia per the American College of Rheumatology criteria (2011) were recruited. The Revised Fibromyalgia Impact Questionnaire with an integration of Soreness Assessment (FIQRS) was established by adding five items pertinent to soreness sensation to the existing FIQR. The participants were asked to evaluate their soreness symptoms by filling out the FIQRS twice. The test-retest reliability and internal consistency were assessed. Construct validity was evaluated by correlations with the FIQR and fibromyalgia symptom severity (SS) score.

Results: Sixty-two patients with fibromyalgia were recruited, including 57 females (91.9%; mean age: 51.4 years). The intraclass correlation coefficient (ICC) of test-retest reliability was 0.92 for the FIQRS overall score. The Cronbach's α of all the items in the FIQRS was 0.93. The correlation coefficient of the FIQRS total score with the FIQR was 0.97 (p < 0.0001) and that with the fibromyalgia SS scale was 0.52 (p < 0.0001).

Conclusion: The FIQRS has good reliability and internal consistency for the assessment of disease impact on fibromyalgia patients, thus providing a reliable tool for soreness evaluation. Future studies are warranted for further validation regarding its correlation with other psychometric properties and life quality measurements.