Serum amyloid a as a high-resolution indicator of mucosal healing in ulcerative colitis.

BACKGROUND: Endoscopy is the standard for assessing mucosal activity in ulcerative colitis (UC), but reliable biomarkers are needed. This study evaluated serum amyloid A (SAA) as a potential biomarker by comparing it with established markers in UC. METHODS: We retrospectively evaluated 182 patients with UC who underwent blood and stool testing within 14 days of colonoscopy at a tertiary care hospital between April 2017 and January 2025. Patients were classified into 4 groups according to the Mayo Endoscopic Subscore (MES). Baseline characteristics and laboratory and endoscopic variables were compared across groups. RESULTS: Serum SAA levels demonstrated strong positive correlations with leucine-rich α-2-glycoprotein (LRG) (r = 0.752) and C-reactive protein (CRP) (r = 0.717). Significant associations were also observed between SAA and MES, Mayo score, partial Mayo score, and Ulcerative Colitis Endoscopic Index of Severity (UCEIS) (all P < .01). SAA identified active endoscopic inflammation (MES ≥ 2) at a cutoff value of 4.1 mg/L, with an area under the curve (AUC) of 0.813 (95% CI, 0.731-0.894), sensitivity of 0.804, and specificity of 0.741. In addition, SAA differentiated MES 0 from MES 1 at a cutoff value of 2.6 mg/L, yielding an AUC of 0.683 (95% CI, 0.470-0.897), sensitivity of 0.706, and specificity of 0.714. CONCLUSIONS: SAA exhibits diagnostic performance comparable to, and in some respects exceeding, that of established inflammatory biomarkers in UC. Importantly, SAA effectively discriminates between MES 0 and MES 1, supporting its potential role as a sensitive marker of mucosal healing.