Chronic Back Pain Predicts axSpA Among One-Third of Patients in Study

The prevalence of rheumatologist-diagnosed axial spondyloarthritis (axSpA) in patients with between 3 and 24 months of chronic back pain was 30% at 2 years, according to study results published online ahead of print in the Annals of Rheumatology.

“A diagnosis of definite axSpA can be reliably made in nearly one-third of patients with chronic back pain referred to the rheumatologist, but diagnostic uncertainty may persist in 5% to 30% after 2 years,” wrote corresponding author Mary Lucy Marques, MD, of Leiden University Medical Center, in the Netherlands, and study coauthors.

The study included 552 patients younger than 45 years from the SPondyloArthritis Caught Early (SPACE) cohort in Europe. Participants had between 3 and 24 months of chronic back pain of unknown origin at the time of rheumatology referral.

Researchers were interested in the diagnosis of axSpA over 2 years after referral to a rheumatologist. After each baseline, 3-month, 1-year, and 2-year visit, rheumatologists reported a diagnosis of axSpA or non-axSpA along with their level of confidence in the diagnosis, from not confident at all (0) to very confident (10). An axSpA diagnosis with a level of confidence of 7 or higher was considered definite.

Among participants, 32% were diagnosed with definite axSpA at baseline and 30% at 2 years, according to the study. Some 5% of patients had their baseline axSpA diagnosis revised, and another 8% gained the diagnosis, by the 2-year visit.

Meanwhile, another 30% of patients continued to have uncertainty surrounding a potential axSpA diagnosis at 2 years.

HLA-B27 positivity and baseline sacroiliitis magnetic resonance imaging (MRI) imaging best distinguished patients with definite axSpA from patients with definite non-axSpA at 2 years. A good response to nonsteroidal anti-inflammatory drugs and sacroiliitis on MRI most often developed over follow-up in patients with newly diagnosed definite axSpA, the study found. Among the 8 patients with MRI-detected sacroiliitis, 7 were HLA-B27 positive and 5 were men.

“Repeated assessments yield is modest,” researchers wrote, “but repeating MRI may be worthwhile in male HLA-B27-positive patients.”

Reference

Marques ML, Ramiro S, van Lunteren M, et al. Can rheumatologists unequivocally diagnose axial spondyloarthritis in patients with chronic back pain of less than 2 years duration? Primary outcome of the 2-year SPondyloArthritis Caught Early (SPACE) cohort. Ann Rheum Dis. Published online January 17, 2024. doi:10.1136/ard-2023-224959