Achilles enthesitis on physical examination leads to worse outcomes after 2 years of follow up in patients with ankylosing spondylitis from REGISPONSER-AS registry

BACKGROUND: Enthesitis represents one of the most important peripheral musculoskeletal manifestations in patients with axial spondyloarthritis (axSpA). However, studies specifically evaluating Achilles tendon enthesitis and its impact over time are scarce. The objectives of this study were to evaluate the impact of Achilles’ tendon enthesitis found at baseline during physical examination on the outcome measures after 2 years of follow-up in patients with ankylosing spondylitis (AS). METHODS: This was an observational and prospective study conducted during 2 years of follow-up in the REGISPONSER-AS registry. Linear regression models adjusted for age, body mass index (BMI), and anti-TNF intake were conducted to evaluate the association between the presence of Achilles enthesitis at baseline and the patient-reported outcome (PRO) scores at baseline. The impact of this feature on PROs over 2 years of follow-up was evaluated using mixed models for repeated measures adjusted for age, BMI, and anti-TNF intake. RESULTS: Among the 749 patients included, 46 patients (6.1%) showed Achilles’ tendon enthesitis during physical examination at the baseline study visit. Patients with Achilles enthesitis had an increase in the global VAS score, BASDAI, mBASDAI, ASDAS-CRP, and BASFI scores in comparison with patients without this feature. In addition, the mean global VAS, BASDAI, and ASDAS-CRP scores were significantly higher among patients with Achilles enthesitis over the 2 years of follow-up after adjusting for age, BMI, and current anti-TNF intake. The percentage of patients achieving ASDAS low disease activity (ASDAS < 2.1) after 2 years of follow-up was 15.9% and 31.5% for patients with and without Achilles enthesitis, respectively (p = 0.030). CONCLUSIONS: In patients with AS, the presence of Achilles’ tendon enthesitis was associated with worse scores on the outcome measures after 2 years of follow-up, leading to a lower probability of achieving low disease activity.