Lymphopenia: A useful predictor of COVID-19 disease severity and mortality

To detect association of lymphopenia with disease severity and mortality.

Total 874 COVID RT-PCR positive patients admitted to KRL Hospital Islamabad from April 2020 to August 2020 were included in this cross-sectional study. Lymphopenia was defined as <1100 cells/micro-L. WHO categories for disease severity were used. Demographic profile, absolute lymphocyte counts and co-morbidities were recorded. Pearson's Chi Square test was used to see association between lymphopenia and disease severity as well as disease outcome. Regression analysis was used to see whether lymphopenia would predict disease severity. Comparison of means of absolute lymphocyte count in different disease categories was done by ANOVA. Tukey's test range was then used to find the means different from each other. P-value ≤ 0.05 was considered statistically significant.

The mean age of patients was 40 ± 12.3 years. Majority patients (73.9%) were asymptomatic. Lymphopenia was present in 6.9% of total patients. Significant association was found between lymphopenia and disease severity as well as lymphopenia and mortality (< 0.001). Lymphopenia was found to be a predictor of disease severity using regression analysis (< 0.001). Comparison of mean absolute lymphocyte count was significant among disease severity categories (< 0.001). On post-hoc analysis, difference in absolute lymphocyte count was significant moving from asymptomatic to mild and then moderate disease category. However no significant difference was seen in absolute lymphocyte count between moderate and severe categories.

Results are compatible with worldwide studies and lymphopenia is valid as a marker of disease severity and mortality.