Semaphorin 3A in Ankylosing Spondylitis

Background/Purpose: To determine serum semaphorin 3A (Sema 3A) levels in ankylosing spondylitis (AS). Methods: Serum Sema 3A was measured in 46 AS patients and 30 healthy controls (HCs). For the patients, we recorded demographic data, disease activity, functional index & global assessment, detected human leukocyte antigen-B27 (HLA-B27), and measured erythrocyte sedimentation rate (ESR) & C-reactive protein (CRP). Results: Sema 3A was higher in AS patients than in HCs (3.98 ± 2.57 vs. 1.34 ± 0.48 ng/ml, p = 0.013). Area under the curve (AUC) of standard receiver operating characteristic (ROC) has suggested that Sema 3A > 2 ng/ml is better to predict the higher Bath Ankylosing Spondylitis Disease Activity Index (BASDAI, > 4) than ESR or CRP. There were good correlations between higher Sema 3A and uveitis, Schöber's test, as well as interstitial lung disease. AS patients undergoing anti-tumor necrosis factor therapies for 3 months exhibited a positive correlation of change in Sema 3A (δSema 3A) with disease activity fluctuation [δBASDAI, δBath Ankylosing Spondylitis Functional Index (BASFI) and δBath Ankylosing Spondylitis - Global score (BAS-G)]. Conclusion: Serum Sema 3A level was increased in AS patients and was inversely correlated to Schöber's test. Serum Sema 3A is better as a bio-marker than ESR or CRP to correlate with high disease activity in AS patients, and it is also a good indicator for monitoring disease activity and functional status during anti-TNF treatment. Also, Sema 3A may be taken as a predictor for extra-articular presentations in AS, but this needs further study to elucidate.