Bruton’s Tyrosine Kinase in Ankylosing Spondylitis

Prospective case-control study.To explore the role of Bruton's tyrosine kinase (BTK) in ankylosing spondylitis (AS).AS substantially affects patients, impairing range of motion in the whole spine and peripheral joints, as well as overall quality of life. However, surveillance for this condition is limited and biomarkers that can predict disease activity are not well documented.The expression of the BTK gene in peripheral blood mononuclear cells was measured using flow cytometry and real time quantitative polymerase chain reaction (qPCR) in 36 AS patients and 30 healthy controls. Demographic features, Ankylosing Spondylitis Disease Activity Score (ASDAS)-CRP based, Bath Ankylosing Spondylitis Disease Activity Index, Bath Ankylosing Spondylitis Functional Index, HLA-B27, ESR, and CRP were evaluated to identify factors associated with BTK expression. Analyses were performed using Spearman's rank correlation test for continuous data, the chi-test for categorical data, and that between continuous and dichotomous variables was measured using a point-biserial correlation test. The area under the curve (AUC) of the receiver operating characteristic (ROC) curve was used to assess the performance of each candidate biomarker.BTK gene expression was significantly higher in AS patients than in controls (P=0.042) according to qPCR results. BTKY223 was also high in CD19+ peripheral blood mononuclear cells (PBMCs) from AS patients, with CD19+BTKY223+high cells being significantly positive correlated to ESR, CRP, and ASDAS. A negative association was observed between BTK expression and the chest expansion distance. The AUC for CD19+BTKY223+ was larger than that for ESR, but CRP still had the largest area.BTK expression was higher in PBMCs from AS patients when compared to controls, and was associated with a higher disease activity index, inflammatory reactants, arthritis and extra-articular manifestations. These findings suggest that BTK expression may play a crucial role in the inflammatory process in individuals with AS.