Op0060 Which Asdas Cut-Off Corresponds Best to Treatment Intensification in Patients With Axial Spondyloarthritis in Daily Practice?

Background: In patients with axial spondyloarthritis (axSpA) and high disease activity (typically defined as Ankylosing Spondylitis Disease Activity Score ASDAS≥2.1), it is recommended to adapt treatment. However, this recommendation is not always followed in practice. The ASDAS was developed for research, and it is unknown how well it performs in daily practice. Possibly, the cut-off of 2.1 as currently endorsed may be too strict in this setting. Objectives: Our objective was to investigate which ASDAS cut-off values correspond best with treatment intensification (TI) in practice. Methods: Data were used from a prospective multicentre Dutch registry for patients with SpA (SpA-Net). Patients with axSpA and ≥1 ASDAS measurement in 2016-2022 were included. TI was defined as 1) higher dose or frequency of the same drug, 2) switch to another drug or 3) addition of a new drug to the current treatment regime; all due to inefficacy. Only anti-inflammatory drugs (NSAIDs, conventional synthetic DMARDs csDMARDs, biologic DMARD bDMARDs, targeted synthetic DMARDs tsDMARDs, corticosteroids) were considered. Single patients could contribute multiple observations. Number and type of TI events, and ASDAS at time of TI, were described. Receiver operating characteristic (ROC) curve analyses were conducted to estimate the ability of ASDAS to discriminate between TI/non-TI (Area Under the Curve AUC), and to identify the ASDAS cut-off that discriminates best in this real-world population, with corresponding sensitivity and specificity. Analyses were conducted with (1) all observations and (2) the first observation per patient per calendar year (to achieve a balanced number of observations per patient by follow-up duration). Results: In total, 350 patients with 2,265 ASDAS measurements were included. Median follow-up was 2.8 (IQR 1.0-4.4) years. Mean age was 50.9 (SD 14.4) years, 153 (43.7%) were female, and mean ASDAS was 2.3 (SD 1.0). Approximately two-thirds of patients (231/350, 66.0%) were on biological/targeted synthetic DMARDs (b/tsDMARDs) at some point during follow-up. TI was applied after 236/2,265 ASDAS measurements (10.4%). At the time of TI, patients were often already on anti-inflammatory treatment (163/236, 69.1%). TI often involved switching to another drug (typically within the same drug class) or addition of a drug, and the use of csDMARDs and corticosteroids was limited. The mean ASDAS and proportion with ASDAS≥2.1 was higher at TI timepoints than at non-TI timepoints (mean ASDAS: 3.0 SD 1.0 versus 2.3 SD 1.0; ASDAS≥2.1: 199/236 84.3% versus 1,096/2,029 54.0%). When all ASDAS measurements were included for analysis, the ROC AUC was 0.71 (95%CI 0.68-0.75) with an optimal ASDAS cut-off of 2.7 (sensitivity 69%, specificity 66%, Youden index 0.35). Results were similar when only one measurement was used per patient and calendar year (1,153 ASDAS measurements; AUC 0.74, ASDAS cut-off 2.7). Over the years, the optimal ASDAS cut-off varied substantially (from 2.3 to 2.8) and was consistently higher than 2.1 (Table 1). Conclusion: In daily practice, TI is associated with a higher ASDAS cut-off value than the recommended one (≥2.1). Possibly, rheumatologists believe the recommended cut-off to be too stringent or consider other factors than disease activity when making treatment decisions. REFERENCES: NIL. Acknowledgements: Role of the Study Sponsor: this investigator-initiated study was financially supported by UCB Biopharma SRL. UCB Biopharma SRL had no role in the study design, in the collection, analysis or interpretation of the data, or in the writing of this abstract. Disclosure of Interests: Casper Webers: None declared, Rabab Nezam El-Din: None declared, Marin Been: None declared, Harald E. Vonkeman has received consulting fees from AbbVie, Novartis, Pfizer, UCB and Johnson and Johnson, has received unrestricted research grants from Galapagos and Boehringer Ingelheim, Astrid van Tubergen has received consulting fees from Galapagos, Johnson and Johnson, Novartis and UCB, has received unrestricted research grants related to SpA-Net from Novartis, Pfizer and UCB.