Background/Purpose: Enthesitis is the hallmark lesion in Spondyloarthritis (SpA). The Maastricht Ankylosing Spondylitis Enthesitis score (MASES), which assesses 13 enthesitic sites, is the most widely used. Fibromyalgia (FM) is characterized by chronic diffuse musculoskeletal pain and diffuse pain points assessed by the tender points of the ACR 1990 criteria. Coexistence of FM represents a difficulty in the evaluation of enthesitis due to a possible overlap between the tender points of the MASES and the ACR criteria for FM. 

To assess the agreement between the MASES and the tender points of the ACR 1990 FM criteria in a population of patients with axial spondyloarthritis (axSpA).

Methods: Ancillary cross-sectional analysis of the French Predict-SpA study. Patients had a diagnosis of axSpA according to their rheumatologist and an indication to start a TNF blocker (TNFb). All patients were screened for FM according to the FiRST questionnaire, and all patients underwent a physical examination : 18 tender points of the ACR 1990 criteria and the 13 enthesitic sites of the MASES were evaluated in a random order. Analysis: the overlap/agreement between the MASES and the ACR/FM tender points was assessed by the intraclass correlation coefficient (ICC). The agreement for “high” values in both scores (i.e. >6 for MASES and >9 for ACR) was evaluated by the PABAK (Prevalence-Adjusted Kappa). The same analysis was performed in the group of patients with and without concomitant FM. The characteristics of patients with high ACR and MASES scores were compared with the rest of the population by univariate and multivariate analyses.

Results: The study involved 526 patients with axSpA diagnosis, and among them, 202 were screened as FM by the FiRST questionnaire (by a score ≥ 5/6) but only 86/526 (16.3%) fulfilled the 1990 ACR FM criteria. Among the 526 patients, 446 (84.8%) had at least one ACR 1990 point, 423 (80.4%) had a MASES ≥1 and 404 (76.8%) had both at least one ACR 1990 point and a MASES ≥1. The ICC between both scores was 0.7 (95%CI [0.6-0.8]). A total of 77/526 (14.6%) patients had high ACR and MASES scores simultaneously. The agreement for high scores, assessed by PABAK, was 0.7 (95%CI [0.6-0.7]).

Among the 202 patients with concomitant FM, 179 (88.6%) had at least one ACR 1990 point and a MASES ≥1, whereas this was the case for 225/324 (69.4%) of patients without FM. The ICC between both scores was 0.6 (95%CI [0.3-0.8]) and 0.7 (95%CI [0.6-0.8]) for patients with and without FM, respectively. The agreement for high scores assessed by PABAK was 0.5 (95%CI [0.4-0.7]) in patients with FM and 0.8 (95%CI [0.7 – 0.8]) in those without.

Patients with concomitantly high ACR and MASES scores were more often HLAB27 negative (OR (95%CI) = 2.4 [1.3-4.4]), had more often a history of talalgia (OR (95%CI) = 1.9 [1.0-3.5]), a BASDAI at inclusion >4 (OR (95%CI) = 4.2 [1.2-26.6]) and a FM (OR (95%CI) = 3.38 [1.87-6.29]).

Conclusion: These results suggest a great overlap between both scores in patients with axSpA, including in those without concomitant FM. However, the coexistence of FM was associated with the presence of many pain points (both in MASES and ACR). Additional studies assessing the metrological performance of MASES in axSpA patients with concomitant FM seem necessary.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/a-large-agreement-between-the-pain-points-of-the-acr-1990-fibromyalgia-criteria-and-the-mases-enthesitis-score-is-observed-in-patients-with-axial-spondylitis-including-in-patients-without-concomitant/