Which ASDAS cut-off corresponds best to treatment intensification in patients with axial spondyloarthritis in daily practice? A prospective study from a clinical registry

To investigate which Axial Spondyloarthritis Disease Activity Score (ASDAS) cut-off corresponds best with treatment intensification (TI) in daily practice in patients with axial spondyloarthritis (axSpA). Patients from the prospective SpA-Net registry with axSpA and ≥ 1 ASDAS measurement in 2016–2022 were included. TI was defined as (1) increasing dose/frequency of current drug, (2) switching drug(s) or (3) adding drug(s); all due to inefficacy of current treatment and only considering anti-inflammatory drugs. Patients could contribute multiple observations. Receiver operating characteristic analyses assessed the ability of ASDAS to discriminate between TI/non-TI (Area Under the Curve [AUC]), and identify the ASDAS cut-off that discriminated best. In a random subsample, the rationale for treatment decisions was retrospectively analyzed using patient records. In total, 350 patients with 2,191 ASDAS measurements (243 TI events, 11.1%) were included. Median follow-up was 2.8 years. At inclusion, mean age was 48.2 (SD 14.3) years, 152 (43.4%) were female, and mean ASDAS was 2.4 (SD 1.0). The mean ASDAS was 3.0 (SD 1.0) at TI versus 2.3 (SD 1.0) at non-TI timepoints. TI occurred infrequently at ASDAS ≥ 2.1 observations (203/1,266 [16.0%]). Using all observations, the AUC was 0.71 (95%CI 0.68–0.74) with an optimal ASDAS cut-off of 2.7 (sensitivity 69%, specificity 66%). When stratifying by drug exposure or extra-musculoskeletal manifestations, results were similar (ASDAS cut-off 2.6–3.2). The patient record analysis supported the findings. In daily practice, TI is associated with a higher ASDAS cut-off than the recommended one (≥ 2.1). Rheumatologists consider factors beyond disease activity when making treatment decisions.