Traditional diagnostic markers were largely accurate for early diagnosis.

Early diagnosis of axial spondyloarthritis (axSpA) in patients with chronic low back pain is important for the timely initiation of anti-inflammatory treatment. Features contributing to an accurate diagnosis were explored in this multicentre European observational cohort study of 552 adults (mean age, 31 years) with low back pain of unknown cause and three months’ to two years’ duration (mean, 13 months) who were referred by general practitioners to rheumatologists. Initial clinical, laboratory and imaging assessment led to a diagnostic classification at baseline with follow up for two years.

At baseline, axSpA diagnoses were made in 175 patients (32%), of whom most had three or more major or minor diagnostic features (e.g. HLA-B27 positivity, family history, acute anterior uveitis, sacroiliitis on radiography or MRI, elevated inflammatory markers, strong response to NSAIDs, or inflammatory bowel disease). At two years, ‘definite’ or ‘most likely’ axSpA diagnoses were made in 218 patients (40%), including most of the original 175 patients plus an additional 50 patients. A strong response to NSAIDs and a new MRI finding of sacroiliitis best predicted a new diagnosis.

Comment: These patients were referred to a rheumatologist for diagnosis, but a take-home point is that most of these diagnoses could have been made in primary care settings based on the presence of traditional axSpA features at baseline. For those whose condition is not diagnosed at baseline, serial assessments of NSAID response and noting new-onset sacroiliitis on MRI might be helpful. Although another recent study cast doubt on the value of NSAID response for axSpA diagnosis, that patient population was much different: Mean age was 45 years, and mean duration of back pain was 15 years (NEJM JW Gen Med Apr 1 2024 and J Rheumatol 2024; 51: 250-256).

Thomas L. Schwenk, MD, Professor Emeritus, Family and Community Medicine, University of Nevada School of Medicine, Reno, USA.

Marques ML, 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 2024; 83: 589-598.

This summary is taken from the following Journal Watch titles: General Medicine, Ambulatory Medicine.