Background: Delay to diagnosis for axial spondyloarthritis (axSpA) remains protracted with a global mean diagnostic delay of 7.4 years [1]. This is due to multiple factors including limited access to rheumatologists (e.g. workforce supply/demand gap; prolonged wait times for specialist consultation; geographic disparity of specialist care) and challenges amongst primary care providers (PCP) in the differentiation of inflammatory back pain from mechanical back pain. The UHN Spondylitis Screening Clinic (SSC) within the Schroeder Arthritis Institute located in Toronto, Canada has implemented an innovative, interprofessional model of care focused on early detection of axSpA. This model of care uniquely leverages Advanced Clinician Practitioner in Arthritis Care (ACPAC)-trained extended scope providers and rheumatology fellows as screeners and has led to substantial improvements in timeliness of axSpA diagnosis, including reducing the average time to diagnosis for non-radiographic axSpA to approximately two years [2]. The FASTRAX study builds on the SSC’s existing body of research aimed at improving access to axSpA and rheumatology care and has expanded with sites across Ontario (Canada’s most populous province) that include Toronto, Ottawa, and Thunder Bay.

Objectives: To evaluate the screening model with respect to 1) referral wait times from PCP referral to rheumatology screening; 2) geographic reach of the program across Ontario; 3) time to axSpA diagnosis; 4) precision and accuracy of the screening process, and 5) number needed to screen to diagnose one patient with axSpA.

Methods: Adults (≥18 years) with low back pain >3 months duration, onset age <50 years were referred by their PCP, physician specialist (e.g. ophthalmology, gastroenterology) or through the provincial low back pain program ( https://lowbackrac.ca ) to their nearest FASTRAX study site for axSpA screening. Screeners performed standard of care assessment. All patients screened were reviewed by an attending rheumatologist with expertise in spondyloarthritis. Screeners and attending rheumatologists indicated risk of axSpA on an 11-point scale (-5, high confidence not axSpA to +5, high confidence axSpA). Risk assignment was dichotomized to negative or positive risk of axSpA. The rheumatologist provided final diagnosis for all patients. Referral wait times (days) were calculated from date of receipt of referral to date of first available consultation. Geographic reach was estimated based on the forward sortation area of the referring provider’s postal code to the site where the referral was accepted. Time to axSpA diagnosis (years) was based on duration of back pain to diagnosis. Prevalence of axSpA was calculated as the number of axSpA diagnoses/total number of patients screened. Sensitivity and specificity were calculated for the screener’s assignment of risk against the gold standard of the rheumatologist’s diagnosis. Number needed to screen (NNS) was calculated as 1/(prevalence of axSpA in the screening model * sensitivity of the screener).

Results: From May 2024 to December 2025, 179 patients completed the screening process across the 3 FASTRAX study sites with a mean (SD) age of 39.5 (9.6) years; 42.4% were male; mean (SD) duration of back pain was 10.9 (10.6) years. Median wait time to assessment was 28 (interquartile range 17-61) days. Geographic reach of referring providers spanned 208, 600 km ² , with referrals from rural and remote regions accounting for 2.8% (Toronto), 14.7% (Ottawa) and 25.6% (Thunder Bay). Across all sites, 41 patients were diagnosed with axSpA, for a study prevalence of 22.9%. Mean (SD) time to diagnosis was 12.1 (12.7) years for patients diagnosed with axSpA. Overall sensitivity and specificity of the screener’s assignment of axSpA risk was 90.2% (95% CI: 85.9% to 94.6%) and 76.6% (95% CI: 68.7% to 84.6%), respectively, with 100% sensitivity observed at Thunder Bay, 92.3% sensitivity at the Toronto site, and 88.0% sensitivity at the Ottawa site. Overall NNS across the province was 5 patients with chronic back pain to identify one patient with axSpA, with a NNS of 4 patients at Ottawa, 5 patients at Thunder Bay, and 8 patients at the Toronto site.

Conclusions: The FASTRAX study of the SSC model for axSpA uniquely leverages ACPAC-trained extended scope providers and rheumatology fellows to expeditiously screen patients with chronic low back pain for axSpA. The model is valid, efficient and demonstrates quick access to care, with referral wait times less than the provincial median wait times [3]. In addition, this model demonstrates vast geographic reach, including rural and remote areas of the province. Historically, axSpA represents approximately 5% of the chronic back pain population, indicating the NNS to detect one axSpA case would be 20 [4]. Using our model the NNS to detect one axSpA case is reduced to 5. Time to diagnosis currently remains prolonged despite shortened time to rheumatology consultation but is expected to decrease as the model expands, gains awareness amongst referring PCPs and matures over time allowing for more targeted rheumatology referrals.

REFERENCES: [1] Poddubnyy D, Garrido-Cumbrera M, Sommerfleck F, et al. Diagnostic delay in patients from the International Map of Axial Spondyloarthritis: geographic, sociodemographic and disease-related factors. Rheumatology (Oxford). 2025 Apr 1;64(4):1873-1879.

[2] Passalent L, Sundararajan K, Perruccio AV, et al. Bridging the Gap Between Symptom Onset and Diagnosis in Axial Spondyloarthritis. Arthritis Care Res (Hoboken). 2022 Jun;74(6):997-1005.

[3] Widdifield J, Bernatsky S, Thorne JC, et al. Wait times to rheumatology care for patients with rheumatic diseases: a data linkage study of primary care electronic medical records and administrative data. CMAJ Open. 2016 May 11;4(2):E205-12.

[4] Reveille JD, Witter JP, Weisman MH. Prevalence of axial spondylarthritis in the United States: estimates from a cross-sectional survey. Arthritis Care Res (Hoboken). 2012 Jun;64(6):905-10.

Acknowledgments: NIL.

Disclosure of Interests: Laura Passalent AbbVie, Novartis, UCB, UCB, UCB, Evelyne Gendron Novartis, UCB, AbbVie, UCB, Tina Chim: None declared, Ngai Chow: None declared, Anne MacLeod UCB, Marcia Correale UCB, Ricardo Sabido-Sauri: None declared, Ozun Bayindir Tsechelidis: None declared, Wesley Fidler UCB, UCB, Raja Rampersaud: None declared, Sibel Aydin AbbVie, UCB, Novartis, Lilly, Janssen, Pfizer, AbbVie, UCB, Novartis, Lilly, Janssen, Pfizer, Nigil Haroon AbbVie, Amgen, Janssen, Lilly, Novartis, Pfizer, UCB, AbbVie, Amgen, Janssen, Lilly, Novartis, Pfizer, UCB, AbbVie, Amgen, Janssen, Lilly, Novartis, Pfizer, UCB, Robert Inman AbbVie, Novartis, UCB, Janssen, Novartis.