Serum Amyloid A as a non-invasive predictive biomarker of mucosal healing in ulcerative colitis patients

Ulcerative colitis is a chronic immune-mediated inflammatory condition of large intestine that is frequently associated with inflammation of the rectum but often extends proximally to involve other areas of the colon. The ultimate target of therapy is complete healing in the form of clinical remission, complete endoscopic and histological healing, and transmural healing for which endoscopy is mandatory. Colonoscopy may not always be applicable due to possible complications in active ulcerative colitis. Therefore, non-invasive biomarkers are needed to avoid the disadvantageous complications of invasive diagnostic procedures. The aim of this study was to evaluate the role of serum Amyloid-A (SAA) as a non-invasive predictive biomarker of mucosal healing in comparison to different laboratory biomarkers, and endoscopic activity scores. The study included 100 ulcerative colitis patients classified into two groups: 50 patients in clinical, and biochemical remission and 50 patients in activity. Complete blood picture, C-reactive protein, erythrocyte sedimentation rate, fecal calprotectin, and SAA were measured and recorded, colonoscopies with histopathological examination were done for all patients. SAA levels were significantly higher in patients with active ulcerative colitis than in clinical remission patients (p < 0.001). In clinical, remission patients without full mucosal healing, SAA was positively correlated with endoscopic disease activity represented with Mayo score, Mayo endoscopic sub-score and Ulcerative Colitis Endoscopic Index of Severity (UCEIS) (p < 0.001). However, there was no significant correlation between SAA and endoscopic scores among the activity patients' group. The cut off value of SAA for determining disease activity was > 5.199 µg/ml with 100 % sensitivity, specificity of 92 %, and accuracy of 99.6%. In conclusion, SAA can be used for prediction of mucosal healing in ulcerative colitis remission patients despite not being superior to fecal calprotectin. However, it was unable to differentiate between the different disease activities or extents.