Predictive Value of the Platelet Times Neutrophil-to-Lymphocyte Ratio (SII Index) for COVID-19 In-Hospital Mortality.

Objective: The performance of the platelet times neutrophil-to-lymphocyte ratio, namely systemic immune inflammation (SII) index, is an inflammatory index that shows controversial results as a predicting indicator of the poor outcomes of COVID-19. In this study, this indicator was analyzed in 3280 patients admitted at a COVID-19 reference hospital in Quito (Ecuador).

Methods: The Receiver Operating Characteristic (ROC) curve analysis was conducted on SII values upon admission to identify the most appropriate cut-off values in discriminating COVID-19 severity and in-hospital mortality.

Results: SII was higher in both severe patients and in those who finally died (cut-off points of 757.3 and 808.5 respectively). However, the AUC-ROC analysis (0.60-0.67) demonstrated a modest discriminating performance of SII for COVID-19 severity (61.2% sensitivity and 61.5% specificity), which sensibly improved for COVID-19 mortality (AUC-ROC: 0.73-0.83, sensitivity: 80.6% specificity; 63.6%).

Conclusion: SII index may well be an indicator of inflammatory conditions secondary to COVID-19 leading to a higher mortality, rather than a predictor of severe forms of the disease.