Performance of 3 Enthesitis Indices in Patients with Peripheral Spondyloarthritis During Treatment with Adalimumab.

OBJECTIVE To evaluate the validity of enthesitis indices in patients with peripheral spondyloarthritis (pSpA). METHODS The ABILITY-2 study evaluated the efficacy of adalimumab (ADA) versus placebo (PBO) in patients with active pSpA over 12 weeks. Patients received open-label ADA for an additional 144 weeks. Twenty-nine enthesitis sites used in 3 enthesitis scoring systems [Leeds Enthesitis Index (LEI), Spondyloarthritis Research Consortium of Canada (SPARCC) Enthesitis Index, Maastricht Ankylosing Spondylitis Enthesitis Score (MASES)] were assessed; discriminatory capacity and treatment response at Week 12 were calculated by standardized mean difference (SMD) and Guyatt's effect size (ES). Sites showing resolution or new-onset enthesitis from baseline to Week 12 were analyzed. RESULTS Overall, 165 patients (ADA, n = 84; PBO, n = 81) were randomized; 143 had ≥ 1 enthesitis site at baseline. The LEI (SMD -0.73, ES -1.07) and SPARCC (SMD -0.56, ES -0.99) enthesitis indices showed higher discriminatory ability and treatment response than MASES (SMD -0.32, ES -0.81). At Week 12, among sites that were positive at baseline, significantly more (p < 0.05) showed resolution among patients treated with ADA versus PBO in the Achilles tendon (60.4% and 36.5%, respectively), medial epicondyle (73.2%, 48.7%), lateral epicondyle (80.6%, 52.8%), and iliac crest (73.5%, 47.2%). Among negative sites at baseline, significantly less (p < 0.05) new-onset enthesitis was observed with ADA versus PBO for Achilles tendon (3.6% and 10.9%, respectively), greater trochanter (3.4%, 14.4%), lateral epicondyle humerus (4.7%, 15.1%), medial femoral condyle (1.6%, 9.2%), and quadriceps insertion superior patella (1.5%, 7.0%). CONCLUSION The LEI and SPARCC enthesitis indices showed better discriminatory capacity and treatment response in patients with pSpA versus MASES, likely because these indices contain more peripheral sites. TRIAL REGISTRATION NUMBER ClinicalTrials.gov NCT01064856.