Purpose: This study was conducted to compare the validity of the Chonnam Modified Early Warning Score (C-MEWS) and other well-known tools used in hospitals to detect deterioration of patients’ condition early for various clinical outcomes, and to identify the most accurate predictive tool. Methods: This is a methodological study to identify and compare the accuracy of different tools using the electronic medical record data of 464 patients admitted to the cardiology department from September to December 2021. To compare the accuracy of C-MEWS, National Early Warning Score (NEWS) and Modified Early Warning Score (MEWS) were selected. We compared the sensitivity, specificity, positive and negative predictive value, and Youden index of these three tools for intensive care unit (ICU) admission, cardiopulmonary resuscitation (CPR) occurrence, in-hospital mortality, and any poor clinical outcomes, respectively. The area under the receiver operating characteristic curve (AUC) was calculated to find the best tool and cut-off for predicting any poor clinical outcome. Results: C-MEWS had Youden index of 0.55, 0.34, 0.54, and 0.60 for ICU admission, CPR occurrence, in-hospital mortality, and any poor clinical outcomes, respectively. The Youden index of NEWS for each clinical outcome was 0.6...