Tehran University of Medical Sciences Acta Biochimica Iranica 0001-5261 1 3 2023 12 01 133 138 Hossein Hosseini Department of Clinical Biochemistry, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran Marzieh Rohani-Rasaf Department of Epidemiology, School of Public Health, Shahroud University of Medical Sciences, Shahroud, Iran Akram Vatannejad Department of Comparative Biosciences, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Asma kheirollahi Department of Comparative Biosciences, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Maryam Shabani Department of Clinical Biochemistry, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran Maryam Teimouri Department of Clinical Biochemistry, Faculty of Medicine, Shahroud University of Medical Sciences, Shahroud, Iran 2023 12 21 Objectives: Recently, the counts of leukocyte subtypes to HDL-C concentration ratios, including monocyte to HDL-C ratio (MHR), neutrophil to HDL-C ratio (NHR), lymphocyte to HDL-C (LHR) have been proposed as potential new indices of inflammation. This study aims to investigate the correlation between these indices with the severity and mortality of COVID-19. Methods: This study is performed on 1224 non-vaccinated and hospitalized COVID-19 patients. The association between blood parameters and indices on admission with severity and mortality are analyzed using multivariate regression models. Receiver operating characteristic curves are used to compare the utility of different blood parameters. Results: The severe patients and deceased groups show low level of HDL-C, high values of WBC, neutrophil, monocyte, eosinophil, WBC/HDL-C, NHR, MHR, LHR, and EHR compared with the mild and survivor groups, respectively (P < 0.05). Multivariate regression analysis reveals that high levels of WBC, neutrophil, WBC/HDL-C, NHR, MHR, EHR, and low levels of HDL-C are still independently associated with severity and mortality after adjusting for age, gender, and comorbidities. The correlation of LHR with severity and mortality is attenuated to insignificance. Also, patients with high eosinophil and monocyte levels have a higher risk of severe disease. According to the AUC values, the best predictors for severity are the level of WBC, neutrophil, and NHR (AUC: 0.724, 0.725, 0.724 respectively), and the best predictors for mortality are WBC/HDL-C and NHR (AUC: 0.788, 0.790 respectively). Conclusion: In summary, low level of HDL-C and high level of WBC, neutrophil, WBC/HDL-C, NHR, MHR, and EHR which can be easily calculated from the CBC and HDL-C concentrations, may provide valuable and readily available prognostic information for severity and mortality of COVID-19. https://abi.tums.ac.ir/index.php/abi/article/view/51 https://abi.tums.ac.ir/index.php/abi/article/download/51/26