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.