Evaluation of the patient acceptable symptom state as an outcome measure in patients with ankylosing spondylitis: data from a randomized controlled trial

Abstract

Objective: To evaluate the feasibility/acceptability, reliability, external validity, and discriminant capacity of the Patient Acceptable Symptom State (PASS) concept in patients with active ankylosing spondylitis (AS).

Methods: PASS was assessed by asking patients to respond yes or no to a single question: "Considering all the different ways your disease is affecting you, if you would stay in this state for the next months, do you consider that your current state is satisfactory?" during the 24-week, randomized (2:1 ratio), double-blind, placebo-controlled portion of an adalimumab study of 315 patients.

Results: PASS reliability was high (kappa = 0.86) in patients with stable disease. Significantly more patients who answered yes to PASS than patients who answered no to PASS were responders based on the ASsessment in Ankylosing Spondylitis (ASAS) International Working Group criteria for 20% improvement (75% who answered yes versus 29% who answered no), the ASAS criteria for 40% improvement (61% versus 16%), the ASAS partial remission criteria (37% versus 3%), and > or =50% improvement on the Bath Ankylosing Spondylitis Disease Activity Index (65% versus 19%; P < 0.001 for all comparisons), demonstrating external validity of the PASS concept. More adalimumab-treated than placebo-treated patients achieved PASS at week 12 (42.3% versus 22.4%; P < 0.001), and more adalimumab-treated than placebo-treated patients achieved sustained PASS through week 20 (34.6% versus 12.3%; P < 0.001), indicating excellent discriminant capacity.

Conclusion: PASS is a feasible, acceptable, reliable, and valid assessment of satisfactory health state in patients with AS.

Trial registration: ClinicalTrials.gov NCT00085644.