Laboratory Markers and Mortality in Novel Coronavirus Disease 2019 (COVID-19): A Systematic Review and Meta-Analysis

Background: Novel coronavirus disease 2019 (COVID-19) is associated with high mortality. Many laboratory values have been suggested to predict patients at risk for a poor outcome in COVID-19.The objective of this project was to systematically review and meta-analyze all laboratory markers associated with prognosis of mortality in patients with COVID-19. Methods: We searched OVID Medline, SCOPUS, MedRxIv, preprints.org, and Centers for Disease Control databases from November 2019 to April 10, 2020 for articles on laboratory values and mortality in COVID-19 and updated the search July 20, 2020. Teams of 2 independent reviewers reviewed titles and abstracts for studies that reported mortality and laboratory values and subsequently abstracted relevant data. Results: Our initial search identified 6,973 articles and a total of 96 articles (30 articles from first search and 66 from updated search) on 72 laboratory values were included. Many laboratory values were associated with mortality, but those most associated with mortality included lymphopenia (OR 0.30, 95% CI 0.24-0.36), thrombocytopenia (OR 0.46, 95% CI 0.35-0.60), elevated lactate dehydrogenase (OR 7.32, 95% CI 5.19-10.33), and ferritinemia (OR 5.19, 95% CI 3.07-8.62). All cardiac markers were associated with mortality, with troponin being the least associated. A low PaO2:FiO2 ratio was also associated with mortality (OR 0.13, 95% CI -0.06-0.28). Heterogeneity was high and risk of bias was moderate. Conclusions: This meta-analysis identified many laboratory abnormalities associated with mortality in COVID-19, though was limited by heterogeneity. Laboratory markers previously identified as associated with a poor prognosis in COVID-19 were confirmed to be those most associated with mortality in this large meta-analysis.