AJCP / ORIGINAL ARTICLE Clinical Significance of CBC and WBC Morphology in the Diagnosis and Clinical Course of COVID-19 Infection Olga Pozdnyakova, MD, PhD,1,2 Nathan T. Connell, MD, MPH,2,3, Elisabeth M. Battinelli, MD, PhD,2,3, 2,3 4 1,2 Jean M. Connors, MD, Geoffrey Fell, MS, and Annette S. Kim, MD, PhD Downloaded from https://academic.oup.com/ajcp/advance-article/doi/10.1093/ajcp/aqaa231/6017543 by guest on 05 December 2020 From the 1Department of Pathology and 3Division of Hematology, Department of Medicine, Brigham and Women’s Hospital, Boston, MA; 2Harvard Medical School, Boston, MA; and 4Department of Statistics, Dana Farber Cancer Institute, Boston, MA. Key Words: Peripheral blood; Morphology; Vacuolization; Monocytes; Atypical lymphocytes; COVID-19; SARS-CoV-2; CBC research parameters; Coronavirus Am J Clin Pathol 2020;XX:1–11 DOI: 10.1093/AJCP/AQAA231 ABSTRACT Key Points Objectives: To investigate the clinical significance of • More severe disease in coronavirus disease 2019 (COVID-19)–positive numeric and morphologic peripheral blood (PB) changes patients was associated with more significant neutrophilia and lymphopenia, while more mild disease was associated with more floridly in coronavirus disease 2019 (COVID-19)–positive abnormal monocyte and lymphocyte morphology. patients in predicting the outcome, as well as to compare • Dynamically, patients who ultimately died became progressively more neutrophilic and lymphopenic from diagnosis until the time of demise. these changes between critically ill COVID-19–positive • Research CBC parameters identified differences in intensive care unit and COVID-19–negative patients. patients with and without COVID-19 infection, suggestive of WBC changes due to SARS-CoV-2. Methods: The study included 90 COVID-19–positive (51 intensive care unit [ICU] and 39 non-ICU) patients and 30 COVID-19–negative ICU patients. We collected Severe acute respiratory syndrome coronavirus 2 CBC parameters (both standard and research) and PB (SARS-CoV-2) is the cause of an ongoing pandemic of morphologic findings, which were independently scored by coronavirus disease 2019 (COVID-19), an acute viral two hematopathologists. illness with a spectrum of disease presentation and se- verity.1 During review of peripheral blood of patients Results: All patients with COVID-19 demonstrated striking with COVID-19 admitted to our hospital, we have numeric and morphologic WBC changes, which were different noticed significant alterations of WBC morphology. between mild and severe disease states. More severe disease While there are an increasing number of publications was associated with significant neutrophilia and lymphopenia, and preprints in peer-reviewed and non-peer-reviewed which was intensified in critically ill patients. Abnormal WBC journals regarding COVID-19 pathogenesis, clinical morphology, most pronounced in monocytes and lymphocytes, presentation, and treatment, the studies that have ad- was associated with more mild disease; the changes were lost dressed the morphologic changes in peripheral blood with disease progression. Between COVID-19–positive and associated with SARS-CoV-2 are all limited to case and COVID-19–negative ICU patients, significant differences in image reports.2-5 The most recent study by Nazarullah morphology-associated research parameters were indicative et al6 that includes a detailed quantitative and quali- of changes due to the severe acute respiratory syndrome tative analysis of peripheral blood changes was con- coronavirus 2 virus, including higher RNA content in ducted on 12 COVID-19–positive patients. In addition, monocytes, lower RNA content in lymphocytes, and smaller very few studies provide correlation between peripheral hypogranular neutrophils. blood WBC morphologic changes and disease out- Conclusions: Hospitalized patients with COVID- comes and address the dynamics of CBC parameters 19 should undergo a comprehensive daily CBC with and morphology.2 manual WBC differential to monitor for numerical and Viral-induced numeric and morphologic changes in morphologic changes predictive of poor outcome and signs the peripheral blood WBC are well characterized in other of disease progression. infections and can direct diagnostic workup to ensure © American Society for Clinical Pathology, 2020. All rights reserved. Am J Clin Pathol 2020;XX:1-12 1 For permissions, please e-mail: [email protected] DOI: 10.1093/ajcp/aqaa231 Pozdnyakova et al / PERIPHERAL BLOOD FINDINGS IN COVID-19 timely therapeutic intervention. For example, in infec- severe sepsis and/or acute respiratory distress syndrome tious mononucleosis, caused by the Epstein-Barr virus, to parallel the respiratory distress found in the COVID- there is a significant lymphocytosis with the presence of 19–positive ICU cohort. Overall, 70% of COVID-19– large atypical lymphocytes, termed Downey cells,7 while negative ICU patients had bacterial infections, with one in human immunodeficiency virus infection, the lympho- patient with concurrent influenza B infection. The under- cytes are morphologically unremarkable in the setting of lying comorbidities included cardiovascular disease (80% lymphopenia.8 of patients), ischemic or nonischemic heart failure (65% This study presents a systematic analysis of pe- of patients), diabetes (25% of patients), and atrial fibril- ripheral blood CBC, including standard and research lation (20% of patients). To ensure there were no other Downloaded from https://academic.oup.com/ajcp/advance-article/doi/10.1093/ajcp/aqaa231/6017543 by guest on 05 December 2020 parameters, as well as morphologic findings in 90 con- hospital-based confounding factors that would have secutive patients with COVID-19. Importantly, the skewed the results, we chose patients who were contempo- study compares the peripheral blood findings between raneously in the ICU with other patients with COVID-19 patients with COVID-19 in the intensive care unit (ICU) (but COVID-19 negative themselves). and non-ICU settings, as well as between COVID-19– Routine CBC with WBC differential was per- positive ICU and COVID-19–negative ICU patients, formed on or near the date of COVID-19 diagnosis and demonstrates significant differences between these (confirmed by SARS-CoV-2 reverse transcription pol- two groups, suggesting an important role of CBC with ymerase chain reaction) and/or admission date (for manual smear review in patient risk stratification. To transferred patients) on Sysmex XN-9000 hematology our knowledge, this is the first study to monitor dy- analyzers as a part of routine clinical care. An auto- namic changes in CBC numeric and morphology mated six-part WBC differential included absolute parameters in COVID-19–positive patients who died of count of lymphocytes, monocytes, neutrophils, eosino- the disease and to investigate morphology-associated phils, basophils, and immature granulocytes, the latter research parameters measured by hematology ana- representing an automated count of promyelocytes, lyzers and compare them between COVID-19–positive myelocytes, and metamyelocytes in peripheral blood. and COVID-19–negative patients. Research parameters associated with neutrophil, lym- phocyte, and monocyte morphology (neutrophil lateral scatter light intensity [NE-SSC], neutrophil fluores- cent light intensity [NE-SFL], neutrophil forward Materials and Methods scatter light intensity [NE-FSC], lymphocyte lateral The study included 90 consecutive patients with scattered light intensity [LY-X], lymphocyte fluores- COVID-19 admitted to our hospital between March cent light intensity [LY-Y], lymphocyte forward scat- 14, 2020, and April 14, 2020, as well as 30 ICU patients tered light intensity [LY-Z], monocyte lateral scattered negative for COVID-19. The study was approved by the light intensity [MO-X], monocyte fluorescent light Institutional Human Research Committee. Clinical pre- intensity [MO-Y], monocyte forward scattered light sentation of patients with COVID-19 varied from mild intensity [MO-Z]), measured on Sysmex-XN hema- to severe disease: 51 patients were admitted to the ICU, tology analyzers but not reported as a part of CBC, and 39 patients were followed in the non-ICU settings. were collected in addition to the routine CBC param- There were no significant differences in underlying eters. WBC morphology was analyzed as changes from comorbidities between COVID-19–positive ICU and normal expected/baseline morphology by two inde- non-ICU patients, with hypertension and cardiovascular pendent board-certified hematopathologists (O.P. and disease being the most common (39% vs 36%, respec- A.S.K.) to review individual abnormal features not tively), followed by diabetes (21% vs 15%, respectively). encapsulated in the differential count and/or the ad- Nonhematologic malignancy was present in 15% in both vanced research parameters. The morphologic changes groups, and hematologic malignancy was present in 12% for neutrophils included toxic granulation, cytoplasmic of ICU patients (6% in remission) and 5% of non-ICU vacuolization, Howell-Jolly body-like inclusions, and patients. Acute kidney injury was present in 6% and Döhle bodies; for monocytes, the changes included the 5%, respectively. Approximately 15% of patients in both presence of large coalescing cytoplasmic vacuoles; for groups did not have significant underlying comorbidities. lymphocytes, the changes included the presence of cy- The ICU patients negative for COVID-19 included toplasmic vacuoles, large granular lymphocytes, and age- and sex-matched