Development of a fibromyalgia-specific quality of life instrument: the Fibromyalgia Quality of Life Scale (FM-QoLS)

Abstract

The study aimed to develop a quality of life (QoL) scale specific to patients with fibromyalgia. The scale development involved four steps: (1) Issue collection, (2) Face validity and selection of the most relevant items, (3) Formation of the preliminary scale and pilot testing, and (4) Psychometric evaluation. For psychometric evaluation, the scale was administered to a sample of fibromyalgia patients. Suitability for exploratory factor analysis (EFA) was assessed using the Kaiser-Meyer-Olkin (KMO) test and Bartlett's Test of Sphericity. Reliability was assessed with Cronbach's alpha, Guttman split-half test, and test-retest correlations. Construct validity was determined via EFA using Principal Axis Factoring. The correlation of the developed scale with established measures of QoL, fibromyalgia impact, fatigue, sleep, and mood was tested to assess convergent validity. Floor and ceiling effects were also examined. The initial item list included 25 issues related to QoL in fibromyalgia. Following the assessments and rating of the initial issue list through cognitive interviews, 10 issues were removed. The remaining questions were administered to 60 patients with fibromyalgia. The final version of the Fibromyalgia Quality of Life Scale (FM-QoLS) contained 14 items and two domains: symptomatology-functionality and psychosocial. Moderate-strong correlations between most items indicated that the scale has a homogeneous structure and measures the same construct. The FM-QoLS showed moderate-strong correlations with pain, anxiety, depression, sleep, fatigue, and established measures of QoL. Regarding the test-retest reliability of FM-QoLS items, the gamma values ranged from 0.923 to 0.995. The FM-QoLS is a 14-item QOL scale specific to patients with fibromyalgia. The scale has high validity and reliability, with no floor and ceiling effects. The FM-QoLS could help physicians address the multifaceted QoL challenges in fibromyalgia patients. Future research could refine the scale by exploring its use in different populations.

Keywords: Fibromyalgia; Quality of life; Reliability; Scale; Surveys and questionnaires; Validation study.