Background Spondyloarthritis (SpA) is a group of disorders that are characterized by inflammatory involvement of the enthesis and the adjacent bone. Enthesitis is regarded as the primary lesion and is observed in all SpA subtypes, and may sometimes be present for several years as an isolated clinical manifestation. Ultrasound is currently considered a powerful tool to identify entheseal affectation, capable of improving the diagnostic accuracy in SpA.
Objectives To evaluate the construct validity of the enthesis ultrasound in the assessment of disease activity in SpA.
Methods A longitudinal Achilles enthesis ultrasound study in patients with early SpA was undertaken. Achilles ultrasound examinations were performed at baseline, six- and twelve-month time periods and compared with clinical outcomes measures collected at basal visit.
Results Bilateral Achilles enthesis of 146 early SpA patients (68 women) were analysed. Basal mean ± SD (range) BASFI, BASRI-spine, BASDAI, and ASDAS were 2.44±2.05 (0-8), 0.67±0.74 (0-3), 4.60±2.07 (0-9.5), 2.51±1.16 (0-5), respectively. Baseline mean visual analogic scale for pain and patient global disease assessment were 5.15±2.5 (range of 0-10) and 2.98±1.56 (range of 0-7), respectively. Mean erythrocyte sedimentation rate was 15.0±16.99 (0-109) mm/h and C-reactive protein was 8.67±16.98 (1-90) mg/l. At baseline Achilles Doppler signal and ultrasound structure alteration were statistically significantly associated with higher CRP and ESR levels. Patients with basal very high disease activity assessed by ASDAS (>3.5) had significantly higher Achilles total ultrasound score verified at baseline (p=0.04); and ASDAS <1.3 predicted no Doppler signal at six and 12 months. Overall, Achilles total ultrasound score per patient was significantly greater in patients with basal higher levels of CRP (baseline p=0.04; six months p=0.006; twelve months p=0.03) and ESR (baseline p=0.02; six months p=0.04; twelve months p=0.005). Doppler signal at basal visit predicted higher total ultrasound score at six and twelve months.
Conclusions Doppler ultrasound seems to be an objective outcome in enthesitis that has significant association with other commonly accepted disease activity measures as ESR, CRP and ASDAS.
Disclosure of Interest None declared