| الوصف: |
Background Axial spondyloarthritis (AxSpA) is a severe and potentially debilitating disease, where earlier diagnosis lead to a better prognosis. Although HLA-B27 antigen is strongly associated with AxSpA, this marker may have a low sensitivity in some Middle-Eastern countries. Recent European studies showed a strong association between antibodies against CD74 and AxSpA with a sensitivity of 85.1%, specificity of 92.2%, and positive likelihood ratio (LR) of 10.8. The diagnostic properties of anti-CD74 may have a particular interest in non-European countries with low HLA-B27 such as Lebanon. Objectives In this prospective study, we tested the diagnostic properties of IgG and IgA anti-CD74 as an early diagnostic marker for AxSpA, compared with HLA-B27, in Lebanon, which is known as one of the countries with the lowest HLA-B27 prevalence ever reported. Methods Sera of AxSpA patients and healthy blood donors (HBD) were analyzed for HLA-B27 genes (PCR) and for IgG and IgA anti-CD74 (ELISA). The patients were recruited from rheumatology clinics across Lebanon. Clinical assessment and sera sample collection were performed at a center specialized in AxSpA (Hotel-Dieu de France University hospital, Beirut). Inclusion criteria were: age 18–45 years, Lebanese, symptom duration Results 29 AxSpA patients and 75 HBD were tested. AxSpA patients were slightly older (31.3 and 27.4 yo, respectively, p=0.02). Male gender was slightly predominant (51.7% and 53.6%, respectively). 93% had all characteristics of IBP as per ASAS criteria. 62.1% had non radiographic AxSpA. Mean disease duration was 25.2 months (SD 15.9), mean BASDAI 4.5 and mean ASDAS 3.25. 58.6% had extra-articular manifestations (28% enthesitis, 24% psoriasis, 21% peripheral arthritis, 10% IBD and 7% uveitis). 27.6% had familial history of SpA (21%), psoriasis (10%) and Crohn9s disease (3.4%). HLA-B27 status was positive in 10 AxSpA patients and in 2 HBD (Sensitivity 34.5%, Specificity 97.2%, Positive LR 12.24). In the ROC analysis, IgG4 anti-CD74 showed the best diagnostic properties for AxSpA (AUC 0.939, cut-off value 0.55). Using this cut-off value, positive values of IgG anti-CD74 were found in 27 axSpA patients and 5 HBD (Sensitivity 93.1%, Specificity 93.3%, positive predictive value 84.4%, negative predictive value 97.2%). Positive LR was 13.97. Anti-CD74 was positive in 58.6% HLA-B27 negative AxSpA (Fig1). Conclusions In this study in a population with low HLA-B27 prevalence, IgG anti-CD74 antibodies showed higher diagnostic value than HLA-B27 for AxSpA. This is of special interest in populations with low HLA-B27 prevalence, especially on the background of diagnosing AxSpA when using the clinical arm of the ASAS classification criteria. Disclosure of Interest None declared |