Clinical Factors Associated with Diagnostic Delay in Axial Spondyloarthritis in Saudi Arabia: A Retrospective Cohort Study

Background/Objectives: Diagnostic delay remains a major challenge in axial spondyloarthritis (axSpA), yet factors associated with delay in Saudi Arabia and the Arabian Gulf remain poorly characterized. We examined clinical factors associated with diagnostic delay in a single-center Saudi cohort. Methods: This retrospective cohort included 160 of 220 screened registry patients with rheumatologist-confirmed axSpA who fulfilled ASAS classification criteria. Diagnostic delay was measured in whole years from documented symptom onset to diagnosis. Twenty-four patients had fibromyalgia documented before axSpA diagnosis. The primary negative binomial model included sex, axSpA subtype, HLA-B27 status, documented prediagnosis fibromyalgia, and symptom-onset age; logistic regression evaluated delay > 5 years. Standardized predictions estimated absolute differences, and a 2-year landmark analysis reduced differential opportunity for fibromyalgia ascertainment. Results: Median delay was 3 years (IQR 2–6), and 41 patients (25.6%) had delay >5 years. Documented prediagnosis fibromyalgia was associated with longer expected delay (ratio of expected diagnostic delays, 1.59; 95% CI 1.24–2.04; p < 0.001), corresponding to an adjusted difference of 2.33 years (bootstrap 95% CI 0.87–4.13), and with greater odds of delay >5 years (OR 5.56; 95% CI 2.08–14.85). Older symptom-onset age was also associated with longer delay. In the landmark analysis (n = 107), fibromyalgia documented by 2 years remained associated with longer subsequent delay (ratio of expected diagnostic delays, 1.51; 95% CI 1.05–2.19; p = 0.027). Conclusions: Documented prediagnosis fibromyalgia and older symptom-onset age were associated with longer diagnostic delay. The fixed-window landmark analysis reduced concern about differential ascertainment opportunity but remained subject to selection and reverse causation and did not establish causality. Persistent features suggestive of inflammatory axial disease in patients with fibromyalgia warrant selective diagnostic reconsideration.