Background: Axial spondyloarthritis (axSpA) often presents atypically in female patients, leading to prominent issues of diagnostic delay. However, the specific determinants of diagnostic delay in women and their impact on 12-month outcomes following treatment initiation remain understudied. This study aimed to identify independent factors associated with diagnostic delay in female axSpA patients and evaluate the independent effect of diagnostic delay on disease activity outcomes at 12 months post-diagnosis.

Methods: This was a single-center retrospective cohort study. We consecutively enrolled 156 female patients diagnosed with axSpA between January 1, 2020, and June 30, 2024. Demographic, clinical, and care pathway data were extracted from medical records. Diagnostic delay was defined as the interval (in years) from symptom onset to definitive diagnosis, analyzed after natural logarithmic transformation. The primary outcome was disease activity at 12 months post-diagnosis, measured by the Ankylosing Spondylitis Disease Activity Score using C-reactive protein (ASDAS-CRP). Univariate and multivariable linear regression analyses were used to identify factors influencing diagnostic delay. Multivariable linear regression (adjusted for baseline ASDAS-CRP, disease phenotype, treatment regimen, and age at onset) assessed the independent impact of diagnostic delay on the outcome.

Results: The median diagnostic delay was 5.90 years (interquartile range: 4.40–7.46). Multivariable linear regression identified that initial consultation with a non-rheumatologist [Beta coefficient (β) = 0.589, 95% confidence interval (95% CI): 0.493–0.686, p < 0.001], prior misdiagnosis (β = 0.218, 95% CI: 0.144–0.292, p < 0.001), non-radiographic axSpA (nr-axSpA) phenotype (β = 0.132, 95% CI: 0.059–0.206, p < 0.001), and concomitant uveitis (β = 0.182, 95% CI: 0.108–0.257, p < 0.001) were independent risk factors for prolonged diagnostic delay. Outcome analysis revealed that, after adjusting for confounders, longer diagnostic delay (β = 0.649, 95% CI: 0.450–0.848, p < 0.001), use of conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) compared to Non-Steroidal Anti-inflammatory Drugs (NSAIDs) monotherapy (β = 0.157, 95% CI: 0.011–0.302, p = 0.036), and higher baseline ASDAS-CRP score (β = 0.481, 95% CI: 0.384–0.578, p < 0.001) were independent predictors of poorer disease control (higher ASDAS-CRP score) at 12 months post-diagnosis.

Conclusion: In female axSpA patients, suboptimal care pathways, misdiagnosis, and atypical clinical manifestations are major contributors to diagnostic delay. A longer diagnostic delay independently predicts worse 12-month treatment outcomes. These findings underscore the urgent need to enhance early recognition capabilities among non-rheumatologists and optimize referral pathways to shorten diagnostic delay.