Serum Activin A Is a Novel Biomarker of Endoscopic Activity in Ulcerative Colitis

Background: Endoscopic healing (EH) is the long-term therapeutic goal for ulcerative colitis (UC). Since repeated colonoscopies are in-convenient and invasive, a surrogate biomarker for endoscopic activity is needed. Activin A is one of the transforming growth factor-beta superfamily of proteins and has been shown to be associated with intestinal inflammation.Methods: This single-center observational study included 27 Japanese patients with UC in clinical remission who underwent colonoscopy and blood sampling. We investigated the correlations between laboratory parameters, including serum activin A levels, and endoscopic activity, classified by the Mayo endoscopic subscore (MES) in these patients.Results: This study included 15 males and 12 females. The median age was 44.0 years. In terms of endoscopic activity, five patients were diagnosed with MES 0, 14 patients with MES 1, seven patients with MES 2, and one patient with MES 3. The median serum activin level was 134.8 pg/mL (interquartile range (IQR), 105.3 -188.1). Serum activin A levels were significantly correlated with the MES (Spearman's rank correlation coefficient r = 0.591, P = 0.001), which was better than that of C-reactive protein (CRP) (r = 0.487, P = 0.010). In the comparison between the EH group (MES 0) and non-EH group (MES 1-3), patients without EH had significantly higher serum activin A levels (Mann -Whitney U test, P = 0.047). A cutoff value of 133.6 pg/mL indicated non-EH with a sensitivity and specificity of 0.682 and 1.000, respectively. The area under the curve (AUC) of serum activin A for detecting non-EH was 0.791 (95% confidence interval (CI), 0.618 -0.964), while that of CRP was 0.723 (95% CI, 0.504 -0.941).Conclusions: The serum activin A level is a potential novel biomarker of endoscopic activity in UC.