Impact of Admission Serum Calcium Level Added on Grace Risk Score for Predicting In-Hospital Adverse Outcome in Patients with Acute Coronary Syndrome

Background: Abnormal calcium metabolism predicts worse outcomes after acute coronary syndrome (ACS). However, this parameter is not included in risk prediction scores, including GRACE risk score. We sought to evaluate whether including serum calcium at admission in a model with a GRACE risk score improves risk stratification. Recently, hypocalcemia has been reported to be an independent predictor of in-hospital adverse outcomes in patients with ACS. Objectives: To assess whether including admission serum calcium value in the GRACE risk score model improves the prediction of in-hospital adverse outcomes in ACS patients. Methods: This prospective observational study was conducted in the Department of Cardiology, Dhaka Medical College Hospital, Dhaka, from May 2019 to April 2020. Patients with ACS were approached for this study according to the inclusion and exclusion criteria. 197 individuals were selected and categorized into two groups: Group A- Those assessed by GRACE risk score with low total serum calcium level (˂2.1 mmol/L), Group B- Those assessed by GRACE risk score alone. In-hospital complications like acute LVF, cardiogenic shock, ventricular tachyarrhythmia, AV block, and deaths were recorded. The predictive values of in-hospital adverse outcomes were compared between the two groups. Data analyses were done using the Statistical Package for Social Science (SPSS) Program version 20.0 for Windows. Results: The mean age of the study population was 56.32 (±10.22) years with clear male predominance (72%). In-hospital complications like acute left ventricular failure, cardiogenic shock, ventricular tachyarrhythmia, and in-hospital mortality were significantly more in patients with on-admission hypocalcemia plus a high GRACE risk score group. Receiver operator characteristic (ROC) curve analysis was performed to compare the predictive efficacy of the GRACE risk score alone and the combination of admission hypocalcemia with the GRACE risk score. The sensitivity and specificity of the GRACE risk score for predicting in-hospital adverse outcomes were 76.2% and 74.5%, respectively. Whereas, after adding admission serum calcium value to the GRACE risk score both the sensitivity and specificity increased to 79.6% and 76.7% respectively. The likelihood ratio for a positive test (LR+) assessed by GRACE risk score (>154) and GRACE risk score (>154) plus on-admission hypocalcemia (<2.1mmol/L) were 2.98 and 3.41 respectively. The likelihood ratio for a negative test (LR-) assessed by GRACE risk score (>154) and GRACE risk score (>154) plus on-admission hypocalcemia (<2.1mmol/L) were 0.31 and 0.26 respectively. The area under the curve (AUC) of in-hospital adverse outcome predicted based on GRACE risk score was 0.798 (P=<0.001, 95% CI: 0.761-0.835) and that based on GRACE risk score + admission hypocalcemia was 0.862 (P=0.016, 95% CI: 0.824-0.901). Multivariate logistic regression analysis determined that low serum calcium level at admission was an independent predictor of in-hospital adverse outcomes in ACS patients (OR= 1.932, 95% CI: 1.089-3.429, P= 0.024). A high GRACE score plus low serum calcium was the most powerful predictor of in-hospital adverse outcomes (OR= 5.345, 95% CI: 1.546-18.480, P= 0.008). Conclusion: A high GRACE risk score plus on-admission hypocalcemia was a strong predictor of in-hospital adverse outcomes in patients with ACS. Therefore, the inclusion of admission serum calcium value into the GRACE risk score could lead to a more accurate prediction of in-hospital adverse outcome