Background Early arthritis is often undifferentiated and may resolve spontaneously, remain undifferentiated, or progress to rheumatoid arthritis or to another chronic joint disease such as SpA. There is a need for improving the early diagnosis of ankylosing spondylitis (AS) and other spondyloarthritis (SpAs).
Objectives To 1- assess the level of agreement between a SpA at baseline and 10 years later in a cohort of patients with recent-onset arthritis and 2- evaluate the ability of baseline clinical, laboratory, and radiographic features to predict a final diagnosis of SpA.
Methods Patients with swelling of at least one joint between 1995 and 1997 were included. Ten years later, the physicians of each patient were contacted to determine the final diagnosis. Baseline pelvic radiographs were subjected to centralized blinded review. The statistical analysis used the chi-square test, Mann-Whitney test, and Cohen’s kappa coefficient.
Results The diagnosis at baseline and 10 years later was known for 164 patients. At baseline, a diagnosis of SpA was suggested in 25 (15.2%) patients, of whom only 10 had a diagnosis of SpA 10 years later, in addition to 10 patients not diagnosed with SpA at baseline (20/164, 12.2%, Kappa=0.36±0.1). The 10-year diagnoses were ankylosing spondylitis (n=3), psoriatic arthritis (n=7), reactive arthritis (n=4), undifferentiated SpA (n=4), SAPHO syndrome, and Crohn’s disease (n=1). Of the 20 patients with a 10-year diagnosis of SpA, only 4 had inflammatory back pain at baseline (versus 11/144 non-SpA patients, p=0.72), 5 had psoriasis (versus 9/144 non-SpA patients, p=0.005), and 1 had uveitis (p=0.12); 10 of the 20 SpA patients were HLA-B27-positive versus 8/144 non-SpA patients (p<0.0001). Blinded review of baseline pelvic radiographs in 12 patients with a 10-year SpA diagnosis showed sacroiliitis in only 2 patients.
Conclusions SpA is relatively rare and extremely challenging to diagnose in patients with early peripheral arthritis.
Disclosure of Interest None Declared