Meeting the ASDAS low-disease-activity target but not symptom-free: item-level residual symptom burden at 12 months in a Saudi axial spondyloarthritis cohort

Abstract Background Treat-to-target management in axial spondyloarthritis (axSpA) is anchored on ASDAS-CRP, with low disease activity (LDA) defined as ASDAS-CRP < 2.1. Meeting this target, however, does not necessarily imply symptom resolution. We examined 12-month responsiveness across individual BASDAI items and described patient-reported residual symptom burden among patients who met ASDAS-LDA at 12 months. Methods We conducted a retrospective analysis of a single-center, IRB-approved Saudi axSpA registry. Adults meeting ASAS classification criteria with complete BASDAI item assessments at baseline and 12 months were included. Changes in the six items were assessed using paired Wilcoxon signed-rank tests with false discovery rate correction and standardized response means. The prespecified primary endpoint was meeting a pragmatic, exploratory residual-symptom criterion, operationally defined as at least one BASDAI item score ≥ 4/10 at 12 months among patients meeting ASDAS-LDA; this threshold is not validated for individual BASDAI items. We also examined a ≥ 5/10 threshold, a prespecified targeted-therapy-exposure subset, baseline-context subgroups, a sensitivity analysis restricted to baseline ASDAS-CRP ≥ 2.1, and exploratory Firth penalized logistic associations, including a model refit after excluding patients classified as having fibromyalgia. Results Among 160 patients, baseline represented first targeted-therapy initiation for 134 (83.8%) and a first eligible routine assessment under NSAID/non-targeted management for 26 (16.3%); no baseline was treatment-switch anchored. All six BASDAI items improved (all q < 0.001), and 102/160 patients (63.7%) met ASDAS-LDA at 12 months; 9/160 (5.6%) had already met LDA at baseline. Of the 102-patient LDA group, 70 (68.6%; 95% CI 59.1–76.8) met the exploratory ≥ 4 criterion and 41 (40.2%; 95% CI 31.2–49.9) met the ≥ 5 criterion. Among 151 patients with baseline ASDAS-CRP ≥ 2.1, 93 (61.6%) attained LDA; 65/93 (69.9%) met the ≥ 4 criterion. Baseline mean item burden was associated with meeting the criterion in the exploratory model (OR 1.79 per point; 95% CI 1.16–2.77), with a similar estimate after excluding patients classified as having fibromyalgia (OR 1.80; 95% CI 1.16–2.80). Conclusions ASDAS-LDA at 12 months frequently coexisted with patient-reported BASDAI item burden. The exploratory item-level criterion does not establish ongoing inflammatory activity or failure of the ASDAS target. These findings support symptom review and mechanism-directed assessment when symptoms persist despite meeting the target.