Reliability, construct validity and responsiveness to change of the PROMIS-29 in systemic sclerosis-associated interstitial lung disease.

OBJECTIVES: PROMIS-29 is a generic health-related quality of life instrument. Our objective was to assess the reliability, construct validity, and responsiveness to change of PROMIS-29 in systemic sclerosis-associated interstitial lung disease (SSc-ILD). METHODS: Seventy-three participants with SSc-ILD were administered patient reported outcomes (PROs) at baseline and follow-up visits which included PROMIS-29 and other measures of generic health, dyspnea, and cough instruments. We assessed internal consistency reliability using Cronbach's α, an alpha of ≥ 0.70 was considered satisfactory. We assessed the responsiveness to change using linear regression models. RESULTS: Mean age of the participants was 51.9 years and the mean disease duration was 7.9 years after first non-Raynaud's symptom. Of the 73 participants, 56.2% were classified as diffuse SSc and 26% limited SSc. The baseline (mean ± SD) FVC % predicted was 73.9±15.5 with a DLCO % predicted of 57.7±21.1; 95.9% had fibrotic NSIP pattern on HRCT. PROMIS-29 scores were 0.2 to 0.9 SD below the US population. Cronbach's α reliability was acceptable for all domains (ranged from 0.77 to 0.98). All scales showed statistically significant correlations with hypothesised PROMIS-29 domains (p≤0.05 for all comparisons). PROMIS-29 showed none-to-small discriminatory ability in comparison with physiologic measures (FVC and DLCO). There was no significant relationship between the change in FVC versus the change in PROMIS-29 measures over time. CONCLUSIONS: PROMIS-29 has adequate reliability and construct validity for evaluation in SSc-ILD. It has moderate-to-large correlations with other PROs. The PROMIS-29 domains were not found to change over time in this cohort, likely due to stable nature of the observational cohort.