A Retrospective Observational Study: Is Absolute Lymphocyte Count a Prognostic Marker in COVID-19?

Abstract

Aim Our study aimed to find a correlation between low absolute lymphocyte count and COVID-19-related mortality. Methods This study followed a retrospective observational cohort design to analyze the data of patients who presented with symptoms and signs of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), at the Conquest Hospital and Eastbourne District General Hospital in East Sussex, United Kingdom, between February 10, 2020 and May 1, 2020, retrospectively. Survival and mortality for the first 30 days and comorbidities were analyzed for all patients who were tested for COVID-19 irrespective of swab results and had blood lymphocyte levels taken at the time of their visit to the ED and their data were analyzed for statistical significance. Results A total of 1226 patients had SARS-CoV-2 RNA identification swabs taken between February 10, 2020 and May 1, 2020. A cohort of 742 patients of these patients tested for COVID-19 also had blood lymphocyte levels measured. Overall, the lymphocyte count did not differ significantly between patients suspected to have COVID-19 infection with either positive or negative COVID-19 swab results. The lymphocyte count, however, was significantly lower in those who died from COVID-19 (p < 0.001) but when comorbidities were analyzed, we found an association between an increased number of comorbidities and a significantly decreased lymphocyte count. Conclusion Once adjusted for comorbidities, the lymphocyte count had no association with COVID-19 infection and mortality.

Keywords: alcohol-related liver disease; copd: chronic obstructive pulmonary disease; covid-19; firth logistic regression models for mortality; lasso model; lymphocyte count; restricted cubic splines; severe acute respiratory syndrome coronavirus-2 (sars-cov-2); stata version 16 (statacorp texas); treat as positive (tap).

Figure 1. Restricted cubic splines for the non-linear association of lymphocyte count with mortality; unadjusted.

Log: Logarithm Loge: Exponent of the log

Figure 2. Restricted cubic splines for the non-linear association of lymphocyte count with mortality; adjusted for age, sex, swab positivity, and comorbidity.

Log: Logarithm Loge: Exponent of the log

Figure 3. Area under the ROC curve for predictive models for mortality in all patients. Model 1 without lymphocyte count and Model 2 with lymphocyte count added.

ROC: Receiver operating characteristic curve.