key: cord-0804193-o6k81dcc
authors: Yip, Christina Y. C.; Yap, Eng Soo; De Mel, Sanjay; Teo, Winnie Z. Y.; Lee, Chun‐Tsu; Kan, Sheryl; Lee, Melvin C. C.; Loh, Will N. H.; Lim, Er Luen; Lee, Shir Ying
title: Temporal changes in immune blood cell parameters in COVID‐19 infection and recovery from severe infection
date: 2020-06-02
journal: Br J Haematol
DOI: 10.1111/bjh.16847
sha: f2a6b4cc42b0157caeaa258b84754bb865971817
doc_id: 804193
cord_uid: o6k81dcc

Since emerging in China in December 2019, the infection caused by SARS-CoV-2, COVID-19, has infected more than 3 million people worldwide (Johns Hopkins University and Medicine: Coronavirus Resource Center). Since then, clusters of infections have emerged in Singapore, particularly among younger workers in communal living environments. The spectrum of COVID-19 infection ranges from mild respiratory illness, to viral pneumonia and life-threatening acute respiratory distress syndrome in up 15-20% (Huang, et al 2020, Wu and McGoogan 2020).

lymphocytes (AS-Lymph). Reference ranges were derived from 120 healthy donors. Statistical analysis was performed by using Stata Statistical Software, release 16.1 (StataCorp., College Station, TX, USA) and the level of significance was set at 5%. Two-sided unpaired t-tests and Mann-Whitney Utests were used for parametric and non-parametric data. Pearson's correlation or Spearman rank correlation was used to assess the associations between variables depending on their normality.

A total of 76 cases, 56 mild, 20 severe/critical (SC), were studied. Three mild cases with no FBC were excluded from the analysis. As shown in Table I , patients in the SC group were older and had a higher incidence of comorbidities. The median day of intubation for SC patients was day 10 of illness and median duration was 11 days. The platelet count was lower and the neutrophil count higher in the SC group than in the mild disease group. The lymphocyte count was significantly lower in the SC group, but RE-Lymph and AS-Lymph subsets were significantly higher in the SC group.

The changes in FBC parameters during infection among SC cases are shown in Fig 1 as median values from illness onset. White blood cell (WBC), neutrophil and platelet counts trended downward to a nadir at day 8-9 of illness but gradually recovered in the subsequent days ( Fig 1A) . The trends of the lymphocyte and lymphocyte subsets (Fig 1B,C) showed that while the lymphocyte count decreased gradually, the proportion of RE-Lymph and AS-Lymph progressively increased towards day 15-16. In mild cases, significant correlations were found between lymphocyte parameters and the day of illness on which the initial FBC was performed. Lymphocyte count (r = 0Á3712, P = 0Á0062), RE-Lymph count (r = 0Á495, P = 0Á002), RE-Lymph% (0Á4639, P = 0Á005) and RE-Lymph as a percentage of lymphocytes (RE-Lymph%/L) (r = 0Á3228, P = 0Á0196) increased with number of days of illness, while no significant correlation was found for WBC, neutrophil, platelet and AS-Lymph parameters.

Among all FBC parameters, AS-Lymph as a percentage of lymphocytes (AS-Lymph%/L) yielded the best area under the receiver operating characteristic (ROC) curve (0Á71) for predicting severe disease. A value >1Á6% gave a sensitivity and specificity of 75% and 67%. A table of the ROC analysis for lymphocyte parameters is presented in the supplementary section (Table S1 ).

The immunopathology of severe COVID-19 is the result of an excessive dysregulated immune response, 5 while correspondence humoral immunity is thought to be essential in controlling the persistent phase of infection. 6 Wang et al. 7 highlighted an association between lymphopenia and severe disease, and our results showed likewise. Additionally, we found that the proportion of activated lymphocytes was clearly higher in severe disease. This increase in AS-Lymph correlates with lymphoplasmacytoid lymphocytes, 8 and CD38 + antigensecreting B cells in patients with COVID-19. 9 AS-Lymph increased particularly in the second week of illness, which parallels seroconversion in the second week as described by Zhao et al. 10 Antibody enhancement may play a role in immunopathology, as higher titres were found in critical cases, 10 and we similarly observed higher AS-Lymph in SC cases. In contrast, Wan et al. 11 noted no difference in total CD19 + B cells. Paradoxically, we also observed that the rise in AS-Lymph predated clinical recovery in several patients, suggesting that functional studies are required to determine if these cells are protective or immunopathogenic in the context of COVID-19. Due to the retrospective nature of our present study, we were unable to serially track FBC changes in mild cases. Our sample size is also not powered to explore independent prognostic biomarkers. However, taken together, our present data show that the FBC and its extended parameters may be a valuable tool to triage patients with COVID-19 and provides evidence to further explore the role of lymphocyte subsets in this disease.

Clinical features of patients infected with 2019 novel coronavirus in Wuhan

Characteristics of and important lessons from the coronavirus disease 2019 (COVID-19) outbreak in China: summary of a report of 72 314 cases from the Chinese Center for Disease Control and Prevention

Novel haematological parameters for rapidly monitoring the immune system response

Identification and quantification of high fluorescence-stained lymphocytes as antibody synthesizing/secreting cells using the automated routine hematology analyzer XE-2100

COVID-19 infection: the perspectives on immune responses

Coronavirus infections and immune responses

Clinical characteristics of 138 hospitalized patients with 2019 novel coronavirus-infected Pneumonia in Wuhan

Hematologic parameters in patients with COVID-19 infection

Breadth of concomitant immune responses prior to patient recovery: a case report of non-severe COVID-19

Antibody responses to SARS-CoV-2 in patients of novel coronavirus disease 2019

Relationships among lymphocyte subsets, cytokines, and the pulmonary inflammation index in coronavirus (COVID-19) infected patients

We thank the departments of Laboratory Medicine of National University Hospital, Ng Teng Fong General Hospital and Alexandra Hospital for supporting the laboratory data collection. We also greatly appreciate the efforts of healthcare workers and the support of their families during this outbreak.