Evaluation and validation of the patient acceptable symptom state (PASS) in patients with ankylosing spondylitis

OBJECTIVE: The Patient Acceptable Symptom State (PASS) constitutes an absolute level of patient well-being and represents an ambitious target for disease management. We explored contributors to PASS, validated the PASS concept, and assessed thresholds of self-reported outcomes below which patients considered themselves in PASS. METHODS: Patients with ankylosing spondylitis completed a questionnaire that included self-reported assessments of pain, fatigue, disease activity, function, patient global, quality of life (QOL), and whether they considered their current disease state satisfactory or not. Stepwise logistic regression was used to assess contributors to PASS. PASS was validated by analyzing proportions of patients reporting need for a rheumatologist and who were in current flare. PASS thresholds for self-reported outcomes were estimated using an anchoring method based on the patient's opinion and targeting the 75th percentile of the cumulative distribution. RESULTS: PASS data were available for 291 patients, of whom 169 (58%) were in PASS. Significant contributors were age (ExpB 1.05; P = 0.003), patient global disease activity (ExpB 0.79; P = 0.008), and function (Bath Ankylosing Spondylitis Functional Index BASFI; ExpB 0.72; P < 0.001). PASS reflected need to consult the rheumatologist and current flare (71% and 73% correctly classified, respectively) and significantly contributed to QOL (B = -5.99; 95% confidence interval -7.16, -4.08). PASS thresholds were 5.0 for patient global disease activity, 5.0 for total back pain, 22.8 for fatigue, 4.8 for disease activity (Bath Ankylosing Spondylitis Disease Activity Index), and 4.0 for function (BASFI). CONCLUSION: A majority of patients (58%) reported being in PASS. PASS thresholds for pain and function were unexpectedly high, possibly suggesting adaptation to the consequences of the disease.