Prevalence of Axial Spondyloarthritis in Young People With Chronic Low Back Pain at a Hospital-Based Health Management Organization: A 10-Year Database Study.

Introduction: There is scarce information on the prevalence of axial spondylarthritis (axSpA) using the Assessment of SpondyloArthritis International Society (ASAS) criteria and even less in Latin America. This study aimed to estimate the prevalence of axSpA by applying the ASAS 2009 criteria to a medical records review study of young people with chronic low back pain (LBP) at a university hospital-based health management organization.

Methods: Electronic medical records from the Hospital Italiano de Buenos Aires health management organization were reviewed to estimate the prevalence of axSpA (radiographic axSpA [r-axSpA] and nonradiographic axSpA [nr-axSpA]) using the ASAS 2009 axSpA criteria in all patients with chronic LBP (≥3 months) aged <45 years at the first LBP appointment, observed between 2009 and 2019.

Results: Among 795 young people with CLBP, the estimated prevalence of axSpA was 5.78% (r-axSpA, 2.76%; nr-axSpA, 3.02%). Ten of 46 patients (21.74%) with axSpA (all nr-axSpA) were undiagnosed, with an undiagnosed axSpA prevalence of 1.26%. The median interval between the first LBP appointment and diagnosis was 34.6 months for axSpA (58.7 vs. 23.1 months for r-axSpA vs. nr-axSpA). Previously diagnosed r-axSpA and nr-axSpA patients had comparable use of biological disease-modifying antirheumatic drugs (bDMARDs) (45% vs. 36%) and delays between nonsteroidal anti-inflammatory drug failure and bDMARD initiation (median, 2.76 vs. 2.66 months).

Conclusion: In our cohort of young persons with chronic LBP, the prevalence of axSpA was approximately 6%, with a high prevalence of undiagnosed axSpA, which could explain the low prevalence of axSpA reported in previous studies in Latin America.