Validity of the PROMIS-29 in a large Australian cohort of patients with systemic sclerosis

Background: We aimed to evaluate the construct validity of the Patient-Reported Outcomes Measurement Information System 29 (PROMIS-29) in Australian systemic sclerosis (SSc) patients. Methods: SSc patients, identified through the Australian Scleroderma Cohort Study database, completed two quality-of-life instruments concurrently, the PROMIS-29 and the Medical Outcomes Study 36-Item Short Form Health Survey (SF-36). The construct validity of the PROMIS-29 was assessed by the correlations between the PROMIS-29 and the SF-36 and Health Assessment Questionnaire Disability Index (HAQ-DI). Cronbach’s alpha was used to test the internal reliability of all instruments in Australian SSc patients and non-parametric correlation, including Spearman’s correlation, was used to test the construct validity of PROMIS-29 against the SF-36 and HAQ-DI. Results: A total of 477 completed questionnaires were returned, equating to a response rate of 59.6%. The mean (±SD) age of respondents at the time of the survey was 64.1 (±11.1) years. They were predominantly female (87.4%), with limited disease subtype (lcSSc) (77.8%) and long disease duration from onset of first non-Raynaud’s phenomenon symptom at the time of survey (10.9 ± 11.1 years). For the correlation analysis between the PROMIS-29 and the legacy instruments, all Spearman correlation coefficients were in the logical direction and highly significant suggesting that the PROMIS-29 is a good alternative to other validated measures of disease burden. Conclusions: Our study indicates that the PROMIS-29 questionnaire is a valid instrument for measuring healthrelated quality of life in Australian females with lcSSc of long duration.