Lymphocyte subsets early predict mortality in a large series of hospitalized COVID-19 patients in Spain

The role of lymphocytes and their main subsets as prognostic factors of death in SARS-CoV-2-infected patients remains unclear, with no information obtained from patients outside China. We aimed to assess whether measuring lymphocyte subpopulations added clinical value to the total lymphocyte counting regarding mortality when they were simultaneously tested at hospital admission. Peripheral blood was analysed in 701 polymerase chain reaction (PCR)-confirmed consecutive patients by lysed-no washed flow cytometry. Demographic and clinical features were registered in electronic medical records. Statistical analysis was performed after a 3-month follow-up. The 112 patients who died were older and had significantly higher frequencies of known co-morbidities than survivor COVID-19 patients. A significant reduction in total lymphocytes, CD3(+), CD4(+), CD8(+) and CD19(+) counts and CD3(+) percentage was found in the group of deceased patients (P < 0 center dot 001), while the percentage of CD56(+)/CD16(+) natural killer (NK) cells was significantly higher (P < 0 center dot 001). Multivariate logistic regression analysis showed a significantly increased risk of in-hospital death associated to age [odds ratio (OR) = 2 center dot 36, 95% confidence interval (CI) = 1 center dot 9-3 center dot 0 P < 0 center dot 001]; CD4(+) T counts <= 500 cells/mu l, (OR = 2 center dot 79, 95% CI = 1 center dot 1-6 center dot 7, P = 0 center dot 021); CD8(+) T counts <= 100 cells/mu l, (OR = 1 center dot 98, 95% CI = 1 center dot 2-3 center dot 3) P = 0 center dot 009) and CD56(+)/CD16(+) NK >= 30%, (OR = 1 center dot 97, 95% CI = 1 center dot 1-3 center dot 1, P = 0 center dot 002) at admission, independent of total lymphocyte numbers and co-morbidities, with area under the curve 0 center dot 85 (95% CI = 0 center dot 81-0 center dot 88). Reduced counts of CD4(+) and CD8(+) T cells with proportional expansion of NK lymphocytes at admission were prognostic factors of death in this Spanish series. In COVID-19 patients with normal levels of lymphocytes or mild lymphopenia, imbalanced lymphocyte subpopulations were early markers of in-hospital mortality.

Automated summary

In this Spanish series, decreased counts of CD4(+) and CD8(+) T cells with an increase in NK lymphocytes at admission were prognostic factors of death in COVID-19 patients. Even in patients with normal or mildly reduced levels of lymphocytes, imbalanced lymphocyte subpopulations were early indicators of in-hospital mortality.