SPARCC, MASES, LEI and MEI Indexes Capture Different Patients with Enthesitis in Axial Spondyloarthritis, Peripheral Spondyloartrhitis and Psoriatic Arthritis

BackgroundSpondyloarthritis, (axial (axSpA), peripheral (pSpA)) and psoriatic arthritis (PsA)) share enthesitis as a hallmark clinical feature. Reliable clinical instruments have been developed to assess enthesitis: Spondyloarthritis Research Consortium of Canada Enthesitis (SPARCC), Leeds Enthesitis Index (LEI), Maastricht Ankylosing Spondylitis Enthesitis Score (MASES) and MEI (Mander Enthesitis Index). Since these four indexes include different enthesis locations, they may capture a different number of patients with enthesitis in the different SpA entities.Objectivesa) To describe the individual locations of enthesitis in axSpA, pSpA and PsA; b) to evaluate whether the prevalence of patients with at least one enthesitis across the three groups differs depending on the use of SPARCC, LEI, MASES and MEI indexes; c) to evaluate the level of agreement between these indexes for detecting patients with at least one enthesitis in axSpA, pSpA and PsA populations.MethodsPerSpA was a multinational observational, cross-sectional study with 24 participating countries worldwide. A total of 4185 patients with a diagnosis of axSpA (2719), pSpA (433) and PsA (1033) according to the Rheumatologist’s opinion were included in this analysis. Information on the location of enthesitis collected during the study visit was used according to the SPARCC, LEI, MASES and MEI indexes.The prevalence of patients with at least one enthesitis according to the different indexes were compared across the diseases (axSpA, PsA and pSpA), and pair-wise agreement between indexes were evaluated using the Cohen’s kappa in the global population and in the three groups.ResultsOut of 36 locations, the most prevalent enthesitis in the overall population were the lumbar spinous processes (6.5%), the thoracic spinous processes (4.9%) and the insertion of the Achilles tendon right (4.8%) and left (3.9%). A total of 10.7%, 8.3%, 13.5% and 17.2% of patients in the overall population showed at least one enthesitis according to the SPARCC, LEI, MASES and MEI indexes, respectively. Figure 1 shows that, among patients with axSpA, MEI and MASES indexes capture the majority of patients with at least one enthesitis (98.7% and 82.4%, respectively), while in pSpA and PsA, MEI and SPARCC are the indexes which capture the majority of patients with enthesitis (100% and 84.6% for MEI and SPARCC in pSpA, and 97.3% and 77% for MEI and SPARCC in PsA, respectively). In PsA, the LEI only captured 57.2% of the patients with at least one enthesitis. In the total population, MASES and MEI showed the strongest agreement for patients with at least one enthesitis (absolute agreement 96.3%; Cohen’s kappa: 0.86). Similarly, among axSpA patients, MASES and MEI showed an almost perfect agreement (97.3%; 0.90), while LEI and MEI showed a moderate agreement (90.4%; 0.54). In pSpA patients, SPARCC and MEI showed the strongest agreement (97.2%; 0.90), as well as among PsA patients (95.4%; 0.82). However, MASES and SPARCC showed a less agreement in PsA patients (94.2%; 0.67).Figure 1.Prevalence of enthesitis captured by different indexes.ConclusionThe most prevalent locations of enthesitis on the global SpA population are the lumbar spinous processes, the thoracic spinous processes and Achilles tendon. MEI and MASES are the two index that capture more patients with enthesitis in axSpA, while MEI and SPARCC are the two index that capture more patients in pSpA and PsA. The LEI index may underestimate the prevalence of enthesitis in these patients. MASES and MEI showed the largest level of agreement in the overall population and in axSpA, while MEI and SPARCC showed the largest level of agreement in pSpA and PsA. These results suggest that the prevalence of enthesitis across entities differs depending on the disease and on the use of the different index.References[1]Heuft-Dorenbosch L, et al. Assessment of enthesitis in ankylosing spondylitis. Ann Rheum Dis 2003;62:127-132Disclosure of InterestsNone declared