key: cord-0901438-pyxzo0cq
authors: Chan, Stephrene S. W.; Christopher, Dheepa; Tan, Guat B.; Chong, Vanessa C. L.; Fan, Bingwen E.; Lin, Clement Y.; Ong, Kiat H.
title: Peripheral lymphocyte subset alterations in COVID‐19 patients
date: 2020-07-01
journal: Int J Lab Hematol
DOI: 10.1111/ijlh.13276
sha: 1b7a00b7a4f27b9928775ae1be5378e680913e00
doc_id: 901438
cord_uid: pyxzo0cq

nan

The novel coronavirus SARS-CoV-2 which causes the acute respiratory illness known as COVID-19 has been characterized by the World Health Organization (WHO) as a global pandemic since March 13, 2020. Despite a lower case-fatality rate, COVID-19 has resulted in significantly more deaths than SARS in 2003, largely in part due to its higher infectivity. As of May 21, 2020, more than 4,800,000 cases of SARS-CoV-2 infection have been confirmed worldwide, with more than 321,000 fatalities. Singapore confirmed its first case of COVID-19 on January 23, 2020. Since then, we have had a total of 29,342 cases and 22 fatalities. Majority of the hospitalized cases were treated at our center, the National Centre of Infectious Diseases (NCID).

Recent studies have shown a decrease in peripheral lymphocytes in COVID-19 patients. [1] [2] [3] We sought to assess the lymphocyte subset alterations in COVID-19 patients, in particular the differences between critically ill patients admitted to the intensive care unit (ICU) and general ward patients. As the number of SARS-CoV-2 infections increases throughout the world, healthcare systems are being overwhelmed. Hence, it is increasingly important to appropriately triage COVID-19 patients and identify those who would need ICU care early.

We retrospectively analyzed 129 samples of ethylenediamine tetraacetic acid (EDTA) anticoagulated peripheral blood samples from a total of 75 patients warded at the NCID, between February 24, 2020, and March 28, 2020. Lymphocyte subsets namely CD3+/ CD4+/CD8+T-cell, CD19+B-cell, and CD16+CD56+ NK cell counts (cells/µL) were measured by multicolor flow cytometry, using the following reagents: human monoclonal anti-CD3-fluorescein isothiocyanate (FITC), anti-CD8-phycoerythrin (PE), anti-CD4-allophycocyanin (APC), anti-CD19-APC, anti-CD16+CD56 PE, and anti-CD45-peridinin-chlorophyll-protein (PerCP) antibodies. Cells were analyzed on a Becton Dickinson FACSCanto TM II Flow analyzer. A complete blood count (CBC) and differential count were also performed on a Beckman Coulter DxH800 analyzer. All non-ICU patients had CBC, differential counts, and lymphocyte sub- In mice depleted of CD8+ T cells, RSV replication in the nose appears to be prolonged. 7 In humans, RSV infection was more severe in immunocompromised children with T-cell defects, and they experienced prolonged viral shedding compared to immunologically normal children. 8 Following natural H7N9 infection, the reduction in IFN-γ + CD8 T cells correlated with clinical recovery. 9 Additionally, we found that NK cells were significantly reduced in ICU patients compared to non-ICU patients and could also be a useful predictor of clinical severity. Our study echoes the findings by Wang F et al, 12 where they described the lymphocyte subsets in COVID-19 and found significantly lower total lymphocytes, CD4+ T cells, CD8+ T cells, and B cells in "severe cases" compared to "mild cases." However, in contrast to our study, the CD4/8 ratio and NK cells were not found to be significantly different between the two groups. Wan S et al 13 showed only statistically significant differences in CD4+ and CD8+

T cells between the "severe group" and "mild group," without any There are several limitations in our study. Firstly, as it is a retrospective study, blood tests were performed sporadically throughout the admission and not at specified time points. Secondly, we acknowledge that treatments administered such as steroids can influence lymphocyte subsets, and this could potentially confound our results. In conclusion, we found statistically significant differences in lymphocyte subsets between ICU and non-ICU patients. We also found that peripheral lymphocyte subset alterations are associated with the clinical severity of SARS-CoV-2 infection. Possible predictors of severity include reduction in CD4+ T cells, CD8+ T cells, and NK cells, as well as an increased CD4/8 ratio.

We thank the Department of Haematology and Department of Laboratory Medicine, Tan Tock Seng Hospital for the full support in the laboratory investigations. Special thanks to Lim Shu Ping and Wong

Lai Har for their assistance with specimen collection and processing. 

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