Can we improve the diagnosis of spondyloarthritis in patients with uncertain diagnosis? The EchoSpA prospective multicenter French cohort.

UNLABELLED: Power Doppler ultrasound (PDUS) has proved to be a highly sensitive tool for assessing enthesitis in spondyloarthritis (SpA). In patients with a suspected SpA, diagnosis could be improved by detecting enthesitis with PDUS.

OBJECTIVE

To evaluate the performance of PDUS for the diagnosis of SpA alone or combined with other clinical, laboratory and imaging findings in patients consulting for a suspected SpA.

METHODS

Prospective, multicenter French cohort study (Boulogne-Billancourt, Brest, Caen, Grenoble, Marseille and Nancy). Outpatients consulting for symptoms suggestive of SpA (inflammatory back pain [IBP], arthritis or inflammatory arthralgia [IA], enthesitis or dactylitis [ED], HLA-B27 positive uveitis [B27+U], familiarity for SpA [Fam]) were recruited and followed up for at least 2 years. Sample size was set to 500 patients (for estimated prevalence of SpA of 30±5% after 2 years). At baseline, patients were submitted to standardized physical examination, pelvic X-ray, sacroiliac joints magnetic resonance imaging (MRI), HLA-B typing, and other tests judged useful for diagnosis. For each patient, a blinded PDUS examination of 14 enthesitic sites was performed at baseline and at years 1 and 2. Patients were planned to be followed during 5 years. The diagnosis of SpA ascertained by an experts' committee, blind to PDUS results, after at least 2 years of follow-up, with a revaluation of doubtful patients at 5 years will be used as gold standard for evaluating the diagnostic performance of PDUS and the best diagnostic procedure by combining PDUS, clinical symptoms and other tests.

RESULTS

Between January 2005 and September 2007, 489 patients were included (96% of the target population). Nineteen patients (0.2%) retired their informed consensus or were lost to follow-up immediately after their inclusion. At baseline, mean age of the 470 remaining patients was 40 years, mean duration of symptoms was 6.1 years; 42% of them were HLA-B27+ and 63% were female. Primary inclusion criterion was IBP in 53%, IA in 27%, ED in 9%, B27+U in 8% and Fam in 4%. Follow-up is still ongoing.

CONCLUSION

We have set up a unique diagnostic cohort which includes the entire spectrum of SpA manifestations. By using PDUS we expected to improve the diagnostic procedure of SpA.