Association Between the C-Reactive Protein-Albumin-Lymphocyte (CALLY) Index and Tissue-Confirmed Cytomegalovirus Colitis in Patients with Active Ulcerative Colitis.

Background: Cytomegalovirus (CMV) reactivation is a clinically important complication in patients with active ulcerative colitis (UC) and has been associated with severe disease activity, treatment refractoriness, and adverse outcomes. The C-reactive protein-albumin-lymphocyte (CALLY) index is a composite biomarker reflecting systemic inflammation, nutritional status, and immune competence. However, its potential role in identifying patients with tissue-confirmed CMV colitis in UC has not been investigated. Methods: This retrospective, single-center cross-sectional study included 82 adults with active ulcerative colitis who underwent tissue evaluation for CMV infection between January 2018 and October 2023. CMV positivity was defined by histopathological and/or immunohistochemical confirmation of CMV infection in colonic biopsy specimens. The CALLY index was calculated as serum albumin × absolute lymphocyte count/C-reactive protein. Receiver operating characteristic (ROC) analysis was performed to evaluate diagnostic performance, and logistic regression analyses were used to identify independent predictors of tissue-confirmed CMV colitis. Results: Eighty-two patients were included, of whom 28 (34.1%) had tissue-confirmed CMV colitis. CMV-positive patients were older and had higher Mayo scores, more extensive disease, lower serum albumin levels, and higher fecal calprotectin concentrations than CMV-negative patients. Although median CALLY index values were numerically higher in CMV-positive patients, the difference did not reach statistical significance (p = 0.136). ROC analysis demonstrated modest discriminative performance for the CALLY index (AUC = 0.601, 95% CI: 0.472-0.722). The optimal CALLY cut-off value of 2838 was derived from the present dataset using the Youden index and yielded a sensitivity of 82.1% and a specificity of 50.0%. In multivariable logistic regression analysis, CALLY ≥ 2838 remained independently associated with tissue-confirmed CMV colitis (OR = 32.09, 95% CI: 3.27-315.39, p = 0.003). Conclusions: The CALLY index demonstrated limited standalone diagnostic performance for identifying CMV colitis in active UC. However, a CALLY value ≥ 2838 was independently associated with tissue-confirmed CMV positivity and may provide complementary information for risk stratification alongside established clinical and inflammatory markers.