increased risk of comorbidities has been reported in Rheumatic and Musculoskeletal Diseases (RMD). We aimed to evaluate the prevalence and pattern of comorbidities in RMD patients nationwide, to identify multimorbidity clusters and to evaluate the gap between recommendations and real screening. Cross-sectional, multicentric nationwide study. Prevalence of comorbidities was calculated according to six EULAR axes. Latent Class Analysis identified multimorbidity clusters. Comorbidities' screening was compared to international and local recommendations. In 769 patients (307 RA, 213 OA, 63 SLE, 103 axSpA, and 83 pSA), the most frequent comorbidities were cardiovascular risk factors and diseases (CVRFD) (hypertension 36.5%, hypercholesterolemia 30.7%, obesity 22.7%, smoking 22.1%, diabetes 10.4%, myocardial infarction 6.6%), osteoporosis (20.7%) and depression (18.1%). Three clusters of multimorbidity were identified: OA, RA and axSpA. The most optimal screening was found for cVRf (> = 93%) and osteoporosis (53%). For malignancies, mammograms were the most optimally prescribed (56%) followed by pap smears (32%) and colonoscopy (21%). Optimal influenza and pneumococcus vaccination were found in 22% and 17%, respectively. Comorbidities were prevalent in RMD and followed specific multimorbidity patterns. Optimal screening was adequate for CVRFD but suboptimal for malignant neoplasms, osteoporosis, and vaccination. The current study identified health priorities, serving as a framework for the implementation of future comorbidity management standardized programs, led by the rheumatologist and coordinated by specialized health care professionals. Rheumatic and musculoskeletal diseases (RMD) are universally prevalent chronic non-communicable diseases (NCD) with a significant contribution to the Global Burden of Diseases 1. They are strong determinants of pain, disability 2-4 and years lived with disability (YLDs) worldwide 5. Many patients experience the concurrent presence of more than one NCD, which is a phenomenon known as multimorbidity 6. NCD may aggregate due to chance-depending on their prevalence in the population-, or due to shared pathophysiologic mechanisms 7,8. They are likely to act synergistically 9 , causing an overall burden that is larger than the sum of their individual impacts. In the general population 6 , four distinct patterns of multimorbidity from chronic NCDs were found: low disease probability, cardio-metabolic conditions, respiratory conditions and RMD and depression pattern, with RMD being highly prevalent across all these patterns. All multimorbidity patterns have a direct association with age and are strongly associated with adverse health outcomes such as long-term disability, frequent healthcare utilization, worsened functional status, poorer quality of life 10 and higher mortality 11,12 .

Aim:To calculate the prevalence of human leukocyte antigen (HLA)-B27 in axial spondyloarthritis patients (axSpA) compared to blood donors (BD) in Lebanon, to identify the clinical and radiological findings associated with HLA-B27 and to estimate the proportion of patients fulfilling the clinical arm of the Assessment of the Spondyloarthritis International Association (ASAS) criteria. Method:Consecutive Lebanese adult axSpA patients fulfilling the ASAS classification criteria were included from 12 rheumatology clinics across Lebanon. BD served as controls. A binary logistic regression was used to study the association between HLA-B27 and the disease features.Results: A total of 247 individuals were included (141 axSpA patients and 106 BD).The prevalence of HLA-B27 was 3.8% in BD and 41.1% in axSpA. Overall, 39.7% of the axSpA patients fulfilled the clinical arm of the ASAS classification criteria.Sensitivity of HLA-B27 for axSpA was 41.1%, specificity was 96.2%, positive predictive value was 93.6%, and negative predictive value was 55.13%. Positive likelihood ratio (LR) was 10.9 and negative LR was 1.63. We found a positive association of HLA-B27 with family history of SpA and psoriasis. Conclusion:Our study confirmed a low prevalence of HLA-B27 in axSpA patients and BD in this Lebanese population, However, we found a high specificity and positive LR, as well as the same number of axSpA patients fulfilling the clinical arm of the ASAS criteria as in European studies. HLA-B27 is therefore valuable for identification of axSpA in Lebanese patients despite the overall low prevalence in this population.Our results may guide future evaluations the role of HLA-B27 in planning local referral strategies.

Axial spondyloarthritis (axSpA) is often diagnosed late due to the non-specific nature of its main symptom [chronic back pain (CBP)] and to the paucity of diagnostic markers, particularly in regions with low HLA-B27 prevalence, such as the Middle-East. We tested the performance of IgG4 and IgA anti-CD74 antibodies as an early diagnostic marker for axSpA, compared with the performance of HLA-B27, in Lebanon. Sera of axSpA patients diagnosed by the rheumatologist and also fulfilling the imaging arm of the ASAS criteria (patients) and of blood donors (BD) (controls) were analyzed for HLA-B27, IgG4 and IgA anti-CD74, blinded to clinical characteristics. Receiver Operating Characteristic curves were constructed to identify an optimal cut-off point for anti-CD74 antibodies. Diagnostic properties were calculated (sensitivity, specificity, positive, and positive predictive values (PPV, NPV), Likelihood ratios) for each marker. Forty-nine axSpA patients and 102 BD were included in the final analysis. IgA anti-CD74 correlated poorly with axSpA (Area Under the Curve (AUC) 0.657), whereas IgG4 anti-CD74 had a good discriminative value (AUC 0.837). Respectively, for HLA-B27, IgG4 anti-CD74, and the combination of both, we found a sensitivity of 33-92-33%, specificity of 96-79-98%, PPV 80-68-89%, NPV 75-95-75%, and LR+ 8.2-4.4-16.5. IgG4 anti-CD 74 were positive in 88% of HLA-B27 negative axSpA patients, and correlated with BASDAI. In this first study in a population with low HLA-B27 prevalence, IgG4 anti-CD74 antibodies combined with HLA-B27 showed higher diagnostic value than HLA-B27 alone for early axSpA. IgG4 anti-CD74 should be considered for further evaluation as an early axSpA diagnostic marker in future dedicated research, particularly in patients with CBP.