Correlation of systemic immune-inflammation index (SII) and ferritin to lymphocyte percentage ratio (FLPR) with neutrophil to lymphocyte ratio (NLR) among patients with severe COVID-19: a retrospective observational study from India

Abstract

Objective: Coronavirus disease 2019 (COVID-19) causes multiorgan dysfunction due to hyperinflammation, dysregulated immune response and cytokine storm. Throughout the COVID-19 pandemic, a number of inflammatory biomarkers, including the neutrophil to lymphocyte ratio (NLR), have been investigated. The aim of this study is to assess the correlation of systemic immune-inflammation index (SII) and ferritin to lymphocyte percentage ratio (FLPR) with neutrophil to lymphocyte ratio among patients with severe COVID-19. Methods: This retrospective observational study was conducted between May 2020 and August 2020 among 55 adult patients (males=35, 65%; females=19, 35%) admitted to intensive care unit (ICU) with severe COVID-19. Neutrophil to lymphocyte ratio (NLR), ferritin to lymphocyte percentage ratio (FLPR), systemic immune-inflammation index (SII) was calculated. Correlation of SII index, FLPR with NLR among severe COVID-19 patients was assessed. Outcome studied was death or recovery and discharge from the hospital. Results: Majority were aged >65 years (n=22, 40%), and diabetes mellitus (DM) was the predominant comorbidity present (n=36, 65.5%). Mean peripheral oxygen saturation (SpO2) on ambient air at admission was 86.8%, mean days of illness from the symptom onset to hospitalization was 6.05 days and average length of stay was 16.22 days. NLR, mean±SD value was 10.17±12.32 and mean value of serum ferritin was 571.27±920.13 (ng/mL). The median (interquartile range, IQR) value of the SII was 1439.17(575.06-3802.05), and the median (IQR) value of FLPR was 28.73 (12.79-62.02). We found a statistically significant correlation between SII and NLR (r=0.926, p=0.0005), FLPR and NLR (r=0.580, p=0.0005) among patients with severe COVID-19. Twenty-six patients recovered (47.3%) and 29 patients died (52.7%). Conclusion: SII and FLPR correlate significantly with most validated inflammatory marker NLR among patients with severe COVID-19.