Assessing health-related quality of life in primary Sjögren's syndrome-The PSS-QoL

Objectives: To develop a questionnaire for the assessment of health-related quality of life (HRQL) in primary Sjögren's syndrome (PSS), and to test its psychometric properties.

Methods: Based on the concepts of a previous qualitative study, a questionnaire for the assessment of HRQL in PSS (PSS-QoL) was developed. Psychometric testing of PSS-QoL was performed after revising the first draft with feedback of patients (n = 6) and clinicians (n = 4). Convergent construct validity was assessed by correlating the score with the EULAR Sjögren's Syndrome Patient Reported Index (ESSPRI), EULAR Sjögren's Syndrome Disease Activity Index (ESSDAI) and Euro-QoL 5D (EQ-5D). Reliability was examined by asking patients to complete the questionnaire twice 1-2 weeks apart. An English Version of the PSS-QoL was developed by using standard methodology with forward and back translation.

Results: Out of the 75 PSS patients, 91% were female, mean (±SD) age was 58.5 ± 12.5 years. PSS-QoL consists of 25 questions and can be divided into two main categories: physical (discomfort and dryness) and psychosocial. The internal consistency of the PSS-QoL revealed a Crohnbach's α of 0.892. Strong and moderate correlations were found between the PSS-QoL and ESSPRI (corr_coeff = 0.755) and EQ. 5D-pain/discomfort (corr_coeff = 0.531). Reproducibility of the PSS-QoL was high, yielding an ICC of 0.958 (95% CI: 0.926-0.981).

Conclusions: The PSS-QoL is the first specific tool for the assessment of patients' HRQL in PSS and showed good psychometric properties. It may serve as a novel patient-reported outcome measure in future clinical studies.