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

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.

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.

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.

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.