Comparison of Blood Counts and Markers of Inflammation and Coagulation in Patients With and Without COVID-19 Presenting to the Emergency Department in Seattle, WA

Christopher M. Chandler, MD; Molly C. Reid, MPH; Sindhu Cherian, MD; Daniel E. Sabath, MD, PhD; Kerstin L. Edlefsen, MD


Am J Clin Pathol. 2021;156(2):185-197. 

In This Article

Abstract and Introduction


Objectives: We compared complete blood count (CBC) with differential and markers of inflammation and coagulation in patients with and without coronavirus disease 2019 (COVID-19) presenting to emergency departments in Seattle, WA.

Methods: We reviewed laboratory values for 1 week following each COVID-19 test for adult patients who received a standard severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reverse transcription polymerase chain reaction (RT-PCR) test before April 13, 2020. Results were compared by COVID-19 status and clinical course.

Results: In total 1,027 patients met inclusion criteria. Patients with COVID-19 (n = 155) had lower leukocytes (P < .0001), lymphocytes (P < .0001), platelets (P < .0001), and higher hemoglobin (P = .0140) than those without, but absolute differences were small. Serum albumin was lower in patients with COVID-19 (P < .0001) and serum albumin, neutrophil to lymphocyte ratio (NLR), and red cell distribution width (RDW) were each associated with disease severity. NLR did not differ between patients with COVID-19 and those without (P = .8012).

Conclusions: Patients with COVID-19 had modestly lower leukocyte, lymphocyte, and platelet counts and higher hemoglobin values than patients without COVID-19. The NLR, serum albumin, and RDW varied with disease severity, regardless of COVID-19 status.


The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in late 2019 in Wuhan, China, and progressed to a pandemic resulting in over 1.7 million global deaths by the end of 2020.[1,2] The clinical disease caused by SARS-CoV-2, coronavirus disease 2019 (COVID-19), has a wide range of clinical manifestations, ranging from asymptomatic to severe pneumonia, acute respiratory distress syndrome (ARDS), and multiorgan failure.[3] Diagnostic testing for the virus is most commonly performed by amplification of viral RNA from nasopharyngeal or lower respiratory tract specimens via reverse transcription polymerase chain reaction (RT-PCR). Early and ongoing limitations on testing hampered disease control efforts. Given the breadth of clinical presentations and widely divergent clinical progression, identifying changes in routine laboratory tests that support the diagnosis and management of patients with COVID-19 is critical.

Early reports from China identified an exaggerated inflammatory response (cytokine storm) as one of the distinct features of SARS-CoV-2 infection, at least in a subset of patients.[4] Significant elevations in serum C-reactive protein (CRP), interleukin 6 (IL-6), ferritin, procalcitonin, fibrinogen, and other acute phase reactants have since been consistently described in patients with severe COVID-19.[5,6] Lymphopenia was singled out as a hallmark of COVID-19 when the first descriptive studies from Wuhan showed that over 80% of patients with COVID-19 had low lymphocyte counts.[5] Other alterations noted on analysis of CBC include leukopenia, eosinopenia, monocytosis, neutrophilia, and thrombocytopenia. The magnitude of lymphopenia and thrombocytopenia in patients with COVID-19 has been associated with more severe outcomes including admission to the intensive care unit (ICU), ARDS, and death. Some have proposed using the neutrophil to lymphocyte ratio (NLR), an established metric of overall inflammatory status, as well as other ratios of hematologic laboratory values as surrogate markers of disease severity in COVID-19.[7–12]

Additionally, a subset of patients with COVID-19 have alterations in coagulation factors manifesting as slightly prolonged prothrombin times (PT), activated partial thromboplastin times (PTT), and increased D-dimer levels, with some COVID-19 patients presenting with coagulopathy and disseminated intravascular coagulation.[13,14] The topic of hematologic and other laboratory alterations in COVID-19 is of considerable interest and has been well reviewed.[15,16] While numerous reports have summarized patterns of laboratory markers in COVID-19 patients and/or identified laboratory markers that correlate with disease severity, comparisons of these markers between patients with and without COVID-19 are infrequent.

We sought to detail differences in CBC with differential in patients with COVID-19 presenting to emergency departments (EDs) affiliated with the University of Washington in Seattle, one of the first metropolitan areas in the United States to encounter SARS-CoV-2 and having one of the first laboratories to receive emergency use authorization from the United States Food and Drug Administration for diagnostic SARS-CoV-2 RT-PCR testing (March 1, 2020). Our data reflect an early time point in the course of the pandemic in the United States, during which differences in treatment approaches between COVID-19 patients is likely to be limited. Importantly, we offer comparison to patients without COVID-19 stratified by clinical course, which captures the diversity of individuals presenting to EDs in the United States.