Integrative Analysis of Neutrophil to Lymphocyte Ratio, CD4+, and CD8+ Cell Counts in COVID-19 Patients: A Retrospective Cohort Study
Authors: Ramirez Claudia M. , Ziad-M. Said Mohamed , Comas-Garcia Andreu , Carmo Pedro , Mendez-Castro Jesus , Varon Joseph 
Published: February 2025

Introduction: Immune dysregulation affecting neutrophils and T-lymphocytes is common in severe coronavirus disease 2019 (COVID-19). This study assessed the association between neutrophil-lymphocyte ratio (NLR), CD4+ and CD8+ counts, and outcomes in COVID-19 patients.

Methods: This is a retrospective study of adult patients admitted to the COVID-19 critical care unit between March 2020 and February 2022. NLR was calculated from leukocyte and lymphocyte count on admission. CD4+ and CD8+ cell counts were also recorded upon hospital admission and at their lowest point during hospitalization. A ROC curve was used to predict mortality risk and determine the best cutoff values for NLR, CD4+, and CD8+. Based on these cutoffs, the patients were divided into groups and then analyzed based on demographic characteristics, severity scores, and laboratory findings. Primary outcomes were the length of stay (LOS), the need for cardiopulmonary resuscitation (CPR), and survival to hospital discharge. Results: For NLR analysis, 985 patients were included. The odds ratio (OR) of death for patients with NLR ≥3.63 on admission was 3.53 (2.51-4.98); p<0.001. The adjusted OR (aOR) of death for these patients was 1.5 (1.003-2.436); p=0.049. 439 (44.5%) patients had NLR ≥3.63, while 546 had NLR<3.63 (55.4%). It was observed that patients with an NLR value of ≥3.63 were more commonly older than 65 years (72%), male (64.7%), and of Caucasian (24.9%) compared to those with an NLR <3.36; p<0.001. To analyze CD4+ cells, 798 patients were included. ROC logistic regression showed that CD4+<200 cells/μl was associated with an increased risk of death. Of these patients, 583 (73.1%) had CD4+≥200 cells/μl, and 215 (26.9%) had CD4+ <200 cells/μl. APACHE II, SOFA, and ICHIKADO CT scores on admission were all higher in the group with lower CD4+ cell counts. This group also had a higher rate of CPR (21.9% vs. 11.0%, p<0.001), LOS (8 days vs. 7 days, p=0.049), and mortality (34.0% vs. 15.1%, p<0.001) when compared to patients with higher CD4+ cell counts. For the analysis of CD8+ cells, 797 patients were included. ROC logistic regression showed that CD8+ <100 cells/μl was associated with an increased risk of death. Of these patients, 628 (78.8%) had CD8+ ≥100 cells/μl, and 167 (21.2%) had CD8+ <100 cells/μl. The group with lower CD8+ cell counts had higher APACHE II, SOFA, and ICHIKADO CT scores, as well as prolonged LOS (9 days vs. 7 days, p<0.001), higher rates of CPR (23.3% vs. 10.5% p<0.001), and higher mortality (41.3% vs. 14.5% p<0.001) when compared with higher CD8+ cell counts.

Conclusions: NLR ≥3.63, CD4+ <200 cells/μl, and CD8+<100 cells/μl on admission were associated with worse outcomes. CD8+<100 cells/μl, along with patient characteristics and biochemical markers, appears to be a stronger predictor of the need for CPR, prolonged LOS, and in-hospital mortality. Additionally, a significant drop in CD4+ or CD8+ levels during hospitalization

Keywords: COVID-19, lymphocytes, CD4+, CD8+, in-hospital mortality, severe acute respiratory syndrome.