Patient Experienced Symptom State in rheumatoid arthritis: sensitivity to change in disease activity and impact.

OBJECTIVES: The Patient Experienced Symptom State (PESS) is a single-question, patient-reported outcome that is validated to assess global disease impact in RA. This study addresses its sensitivity to change, and reliability. METHODS: Disease activity, disease impact in the seven domains of RA Impact of Disease (RAID) and PESS were assessed in patients with RA from the NOR-DMARD registry, at two visits, 6 months apart. The PESS over the last week was scored at five levels, from 'very bad' to 'very good'. Disease impact and disease activity were compared between patients who improved, maintained or worsened PESS over time, through one-way analysis of variance, with post hoc Bonferroni correction. Correlations between changes in these parameters were assessed through Spearman's correlation coefficient. Sensitivity to change was assessed by standardized response mean (SRM) between the two visits. Reliability was analysed through intraclass correlation coefficient (ICC) between the two visits in patients with stable disease activity and impact. RESULTS: In 353 patients [76.8% females, mean (s.d.) 9.9 (9.6) years disease duration], improvement in PESS level was associated with substantial improvements in mean impact in all domains as well as disease activity (P <0.02). PESS change was moderately to strongly correlated with RAID domains and disease activity (rho: 0.4-0.7). PESS was responsive to change (SRM: 0.65, 95% CI: 0.54, 0.76), particularly among RAID responders (SRM: 1.79, 95% CI: 1.54, 1.99). PESS was moderately reliable in patients with stable condition (ICC: 0.72, 95% CI: 0.52, 0.83). CONCLUSION: PESS is valid, feasible, reliable and responsive, representing an opportunity to improve the assessment of disease impact with minimal questionnaire burden.