Context: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a highly infectious agent, with the propensity to cause severe illness. While vaccine uptake has been increasing in recent months, many regions remain at risk of significant coronavirus disease 19 (COVID-19) related healthcare burden. Health systems will continue to benefit from the availability of a variety of clinical and laboratory model when other triaging models are equivocal.

Objective: To validate previously reported clinical laboratory abnormalities seen in COVID-19 patients and identify what laboratory parameters might be outcome-predictive.

Design: We undertook an observational study of hospital-admitted COVID-19 patients (n=113), looking at a broad selection of clinical, laboratory, peripheral blood smear, and outcome data over discrete discovery and validation periods from March 2020 to November 2020.

Results: We confirmed the findings of previous studies noting derangement of a variety of laboratory parameters in COVID-19 patients, including peripheral blood morphological changes. We also devised a simple-to-use decision tree by which patients could be risk stratified on the basis of Red Blood Cell count, creatinine, urea, and atypical plasmacytoid lymphocyte (“covidocyte”) count. This outcome classifier performed comparably to the World Health Organization clinical classifier and the neutrophil-lymphocyte ratio.

Conclusions: Our data add to the increasing number of studies cataloguing laboratory changes in COVID-19, and support the clinical utility of incorporating blood morphological assessment in the workup of hospitalized COVID-19 patients.

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Author notes

*Authors contributed equally.

Dr. Jenei is an employee of CellaVision AB which provided the instrument for this study; CellaVision AB did not provide any financial support or any other payment for this study. Dr. Pillai received financial support received from the Canada Foundation for Innovation and the Canadian Institute of Health Research. The other authors have no relevant financial interest in the products or companies described in this article.