Systemic Sclerosis Quality of Life Questionnaire (SScQoL): translation into Turkish and assessing its psychometric properties

Abstract

Background: Systemic sclerosis (SSc) is a chronic autoimmune disease that affects the connective tissues and leads to physical, emotional, and social challenges for patients. Evaluating health-related quality of life (HRQoL) with a disease-specific tool may be preferable for improving patient care and treatment outcomes. The aim of this study was to translate the Systemic Sclerosis Quality of Life Questionnaire (SScQoL) into Turkish and to investigate its psychometric properties.

Methods: Eighty-six patients with SSc (mean age 51.8 ± 11.7 years, 80 females) participated in the study. Convergent validity was explored by correlation analyses between Turkish SScQoL and Short-Form 36 (SF-36), European Quality of Life Survey-5 Dimensions (EQ-5D), EQ-5D Visual Analog Scale (EQ-VAS), and Scleroderma Health Assessment Questionnaire (SHAQ). Cronbach's alpha was calculated to test internal consistency. Turkish SScQoL was readministered after 7-14 days to fifty-eight patients for determining test re-test reliability. Intraclass correlation coefficients in 95% confidence interval (ICCs [95%CI]) were calculated to examine the agreement between two assessments. Values greater than 15% and an absolute skewness value < 1 were recognized as the presence of a floor or ceiling effect.

Results: SScQoL correlated significantly with SF-36 subdomains (r = -0.347 to -0.618, p < 0.01), EQ-5D (r = -0.535, p < 0.01), EQ-VAS (r = -0.636, p < 0.01), and SHAQ global score (r = 0.521, p < 0.01). SScQoL demonstrated excellent internal consistency (Cronbach's alpha = 0.917), and good to excellent test-retest reliability (ICC [95%CI] = 0.85 [0.76-0.91]). No floor/ceiling effects were observed.

Conclusion: The Turkish version of SScQoL seems to have adequate psychometric properties and can be used to evaluate HRQoL in clinical and research settings. Key points • Turkish version of SScQoL is a valid and reliable tool for measuring health-related quality of life of patients with systemic sclerosis. • SScQoL is the only diseases-specific quality of life measurement for systemic sclerosis available in Turkish. • Patients with limited and diffuse SSc seem to be similar in terms of self-reported health-related quality of life.

Keywords: Health-related quality of life; Reliability; Systemic sclerosis; Validity.