Crucial Laboratory Parameters in COVID-19 Diagnosis and Prognosis: An Updated Meta-Analysis

Abstract

Molecular identification of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the gold-standard for Coronavirus Disease 2019 (COVID-19) diagnosis. However, common laboratory parameters play a pivotal role in case detection and progression monitoring in low-resource settings with limited access to molecular diagnostics. We aimed to summarise current evidence on the differences between common laboratory parameters in COVID-19 and non-COVID-19, and between severe and non-severe COVID-19. PubMed, Scopus, the Chinese Medical Journal Network, Google Scholar, and Web of Science were searched until March 2020. The first analysis included studies comparing between COVID-19 and non-COVID-19 infections, while the second included studies that compare between severe and non-severe COVID-19. Retrieved parameters include leukocyte, neutrophil, thrombocyte, and lymphocyte counts in addition to C-reactive protein (CRP), procalcitonin (PCT) and D-dimer levels. In the presence of heterogeneity, the random-effect model (REM) was used instead of the fixed-effect model (FEM). Eight studies included in the first analysis showed significantly lower leukocyte (p<0.00001), neutrophil (p=0.01) and thrombocyte (p=0.0005) counts in COVID-19 cases. Twenty-eight studies included in the second analysis showed significantly lower lymphocyte (p<0.0001) and thrombocyte (p=0.0002) counts, and significantly higher leukocyte (p=0.01) neutrophil (p<0.0001), D-dimer (p<0.00001), and CRP (p<0.00001) levels in severe COVID-19 cases. Thrombocyte count is key in both diagnosis and prognosis. Low leukocyte and neutrophil counts are markers of COVID-19 infection, but contrastingly higher counts indicate progressive COVID-19. And although lymphocyte, D-dimer and CRP levels did not demonstrate diagnostic value, all indicate severity of COVID-19. Confirmation of these findings should be performed in future studies.