Reliability and Validity of Patient-reported Outcomes Measurement Information System Short Forms in Ankylosing Spondylitis

Objective. To assess the reliability and validity in ankylosing spondylitis (AS) of selected Patient Reported Outcomes Measurement Information System (PROMIS) Short Forms (SF) developed by the US National Institutes of Health. The analysis was done across core sets and patient-identified domains of the Assessment of Spondyloarthritis international Society.

Methods. Participants in the Prospective Study of Outcomes in Ankylosing Spondylitis (PSOAS), an ongoing, prospective longitudinal observational study, completed 6 PROMIS SF assessing global health, depression, fatigue, physical function, pain intensity, and pain interference during their PSOAS visits from September 2017 to January 2019. Test-retest reliability and internal consistency were assessed using intraclass correlation coefficients and Cronbach’s alpha coefficient, respectively. PROMIS SF were compared to legacy measures collected. Construct validity was evaluated through examination of score distributions and floor effects, and through examination of the Spearman correlation coefficients between PROMIS measures and existing legacy AS measures. Discriminant validity was tested across Ankylosing Spondylitis Disease Activity Score (ASDAS) groups.

Results. Participants (n = 119) were mostly male (69%), white (81%), and with a mean (SD) age of 51 (± 15) years. Legacy measures demonstrated floor effects that were not present in PROMIS SF. Good test-retest reliability (r > 0.8) and excellent internal consistency (α > 0.9) was noted in the PROMIS SF. The 6 PROMIS SF correlated moderately to strongly [ρ 0.68 (Depression) to −0.87 (Physical Function)] with appropriate legacy measures. PROMIS scores measures worsened significantly (p < 0.05) with higher ASDAS groups.

Conclusion. This study supports the reliability and construct validity of PROMIS SF to assess AS symptoms from a single-center sample of patients with AS. Further research is needed to test responsiveness, feasibility/resource burden, and different cultural/societal contexts for patients with AS.