Reliability and validity of the PROMIS-29 health profile in Ankylosing Spondylitis patients: A cross-sectional study

The Patient-Reported Outcomes Measurement Information System 29-Item Health Profile (PROMIS-29) is a generic measure of health-related quality of life that is not well-studied in Ankylosing Spondylitis (AS) patients. Our objective was to investigate the reliability and validity of the PROMIS-29 in AS. About 169 consecutive AS patients were enrolled from 2017 to 2022 with 167/169 patients fully completing the PROMIS-29 in this cross-sectional study. Test-retest reliability and internal consistency was assessed using intraclass correlation coefficients (ICC) and Cronbach alpha, respectively. We studied structural validity with confirmatory factor analysis (CFA) of our hypothesized and general population models. We evaluated model fit by Chi-squared goodness-of-fit-test (χ2), comparative fit index, and root mean square error of approximation. A χ2 test was used to compare nested models. PROMIS-29 convergent validity was studied by Spearman correlation coefficients with AS-legacy measures. PROMIS-29 domains showed good test-retest reliability (intraclass correlation coefficients (ICC) > 0.7) and excellent internal consistency with Cronbach alpha > 0.9 in all subscales. CFA of only the general population model met our model fit cutoffs (χ2 goodness-of-fit P-value of 0.21, comparative fit index of 0.99, and root mean square error of approximation of 0.05). Furthermore, a nested χ2 test was not significantly different between our hypothesized (full) and general (reduced) model [χ2 (1) = 0.754, P > .38]. AS legacy measures showed a strong correlation (rho > |0.7|) with the extracted physical health factor. The PROMIS-29 demonstrated good reliability and construct validity in AS patients with the general population model. Further study is required to determine its clinical and research utility in AS patients.