Nutritional Indices as Non-Invasive Biomarkers: PNI and CONUT Scores Predict Clinical and Endoscopic Activity in Ulcerative Colitis

<b><i>Background and Objectives</i></b>: Determination of disease activity is important for appropriate treatment selection and clinical follow-up in ulcerative colitis (UC). Colonoscopic examination is the gold standard in the evaluation of disease activity in current clinical practice. However, colonoscopic procedures are invasive, expensive, and not comfortable for the patients; also, possible complications that may develop during the procedure have led clinicians to seek practical, economical, and reproducible new biomarkers that can be used in the clinical follow-up of UC patients. In our study, we aimed to analyze the relationship between the nutritional markers, such as prognostic nutritional index (PNI) and controlling nutritional status score (CONUT), with clinical and endoscopic activities of the disease in ulcerative colitis disease. <b><i>Materials and Methods</i></b>: The study included 196 patients who were followed up with the diagnosis of ulcerative colitis in the Internal Medicine Clinic and Gastroenterology Outpatient Clinic of our hospital. Demographic data, laboratory parameters, and endoscopy reports of the patients were reviewed retrospectively. Patients were divided into two groups: remission-mild disease and moderate-severe disease in terms of clinical activity, and endoscopic remission and active disease in terms of endoscopic activity. The relationship between the PNI and CONUT scores calculated from the results of the examinations at the hospital admissions with the Mayo score and Rachmilewitz endoscopic activity index scores stated in the endoscopy reports was analyzed. <b><i>Results</i></b>: In our study, 78 (39.8%) cases were female and 118 (60.2%) were male. The mean age was 40.28 ± 13.74 years. According to clinical activity, 90 (45.9%) of the cases had remission-mild disease, and 106 (54.1%) had moderate-to-severe disease. According to endoscopic activity, endoscopic remission was observed in 66 (33.7%) cases, and active disease was observed in 130 (66.3%) cases. PNI score was detected to be statistically significantly lower in the moderate-to-severe clinical activity group and endoscopically active patient group compared to the other groups, while the CONUT score was detected to be statistically significantly higher (<i>p</i> < 0.001; <i>p</i> < 0.001). <b><i>Conclusions</i></b>: PNI and CONUT scores are not only effective predictors of clinical and endoscopic disease activity in UC but also emphasize the critical role of nutritional assessment in the holistic management of inflammatory bowel disease. These findings suggest that integrating routine nutritional screening into gastroenterology practice can provide dual benefits: serving as a non-invasive biomarker for mucosal inflammation and identifying patients who may require early nutritional intervention to improve clinical outcomes.