Lymphopenia: A predictive marker of disease severity in COVID-19 infection

Background. With the latest COVID-19 deaths reported to WHO now exceeding 3.3 million, COVID-19 has developed into a milestone of our medical generation, causing disruption in communities and hospital services. With complications raging from respiratory failure to inflammatory complication and even thrombotic events, we wanted to establish if lymphopenia is a predictive marker of disease severity in patients infected with SARS-CoV-2. Material and methods. 152 patients were included from 4 different departments of Colentina Clinical Hospital in this retrospective observational study beginning with July 2020 to March 2021. All of these patients were confirmed with COVID-19 by real-time reverse transcriptase polymerase chain reaction test for nasal and pharyngeal swab samples. As including criteria we have set the patients hospitalized confirmed with COVID-19, with at least 10 days of hospitalization. The data in demographic, basic clinical and laboratory characteristics and particular evolution was obtained from electronical medical records from each department involved in the study, by maintaining personal data confidentially. We set up criteria for lymphopenia as absolute lymphocyte count below 1.5 x 1000/µl, based on the laboratory reference values. The study group was divided into several groups: male and female, ICU (Intensive Care Unit) and non-ICU, deceased and released, lymphopenia at day 1 (day of admission to hospital) , lymphopenia at day 10 (10 days after hospital admission). Results. The age of the patients ranged from 17 to 92, with the median age of 57.62. Enrolled were 73 (47.4%) female patients and 79 (52.6%) male patients, with an ICU admission rate of 35.71% (55 patients), and a mortality rate of 21.43% (33 patients). Patients who have a severe form of COVID-19 and are admitted to the ICU for mechanical ventilation did not recover and died (p < 0.001). Male patients may have higher risk of requiring admission in ICU (p value = 0.357) and higher risk of death (p value = 0.241). Even in our small group of 152 patients, the elderly patients suffered a more severe form of the disease, which was reflected on the number of admission days (p = 0.07). In our specific population, based on the statistics, if we take the number of lymphocytes on the day of admission as the dependent factor, we can safely say that there is a statistically significant correlation between lymphopenia at day 1 and the ICU admission (p < 0.001) or death (p = 0.014). The number of lymphocytes following 10 days of admission is another prognostic marker as we can see from the results of statistic tests: there is a statistically significant correlation between lymphopenia at day 10 and the ICU admission (p < 0.001) or death (p < 0.001). Age is another predictive factor regarding the number of lymphocytes following 10 days of admission (r = -0.078 and p = 0.356). Conclusion. Lymphopenia is an easy-to-determine, efficient and reliable biomarker to establish the disease evolution in patients with COVID-19