Laboratory parameters and outcomes in hospitalized adults with COVID-19: a scoping review

Background: Laboratory parameters and the associated clinical outcomes have been an area of focus in COVID-19 research globally. Purpose: We performed a scoping review to synthesize laboratory values described in the literature and their associations with mortality and disease severity. Methods: We identified all primary studies involving laboratory values with clinical outcomes as a primary endpoint by performing data searches in various systematic review databases until 10th August, 2020. Two reviewers independently reviewed all abstracts (13,568 articles) and full text (1126 articles) data. A total of 529 studies involving 165,020 patients from 28 different countries were included. Investigation of the number of studies and patients from a geographical perspective showed that the majority of published literature from January–March 2020 to April–June 2020 was from Asia, though there was a temporal shift in published studies to Europe and the Americas. For each laboratory value, the proportion of studies that noted a statistically significant (p < 0.05) correlation with adverse clinical outcomes (e.g., mortality, disease severity) was tabulated. Results and conclusion: Among frequently reported laboratory values, blood urea nitrogen was the most often reported predictor of mortality (91%); neutrophil-to-lymphocyte ratio was the most frequent statistically significant laboratory parameter in predicting disease severity (96%). This review highlights the temporal progression of laboratory value frequencies, as well as potentially distinct utilities of different markers for clinical outcomes of COVID-19. Future research pathways include using this collected data for focused quantitative meta-analyses of particular laboratory values correlated with clinical outcomes of mortality and disease severity.