Association of Mortality with Lymphocyte Subset in Patients with COVID-19-associated Acute Respiratory Failure: A Subgroup Analysis

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes pneumonia and lymphopenia. We investigated the predictive value of T-lymphocyte subset absolute counts for outcomes following coronavirus disease-2019 (COVID-19)-associated acute respiratory failure (C-ARF). Patients and methods: A retrospective chart review of adult patients with C-ARF was undertaken from 23 March 2020 to 20 November 2021 to obtain relevant data. Patients were divided into two groups based on survival. The T-lymphocyte subsets were determined by flow cytometric analysis. A binomial logistic regression was performed to ascertain factors affecting survival. Cut-off values to differentiate between survivors and non-survivors were identified with the receiver operating characteristic (ROC) analysis. Results: A total of 379 patients were analyzed. Age was negatively correlated with survival. Non-survivors had significantly lower T-lymphocyte subset absolute counts than survivors. Serum ferritin levels were significantly higher in non-survivors. Baseline lymphocyte (%) and a subset were predictive of survival in patients [lymphocyte (%) <5.65%, CD3+ <321 cells/mu L, CD4+ <205 cells/mu L, CD8+ <103 cells/mu L]. Conclusions: Lower T-lymphocyte subsets were associated with higher mortality in patients with C-ARF. Monitoring trends may help in identifying patients at increased risk of poor outcomes.