A meta-analysis of 35 studies pinpoints the lab values that could help predict the course of SARS-CoV-2 infection. Lymphocytes, C-reactive protein (CRP), procalcitonin (PCT), D-dimer, and other inflammatory, organ function, and cardiac markers might flag risk and poor outcomes in severely ill patients.

Researchers combed through PubMed and Web of Science articles to find studies on the characteristics of SARS-CoV-2 lab findings, focusing specifically on severe and critically ill patients. In the literature findings, they assessed lab index values, calculating final statistical values. They also compared indexes of severe and non-severe patients and described the combined analysis of different types of indexes crucial to predicting the course of illness.

Lymphopenia was a common finding upon admission among 5,912 patients included in the studies, according to the authors. For this reason, platelet count-to-lymphocyte ratio and the neutrophil/lymphocyte ratio could serve as new indexes for worsening COVID-19.

Blood coagulation changes also have been observed in severely ill COVID-patients. Individuals with severe disease might have raised D-dimer levels, prolonged prothrombin time, and shortened activated partial thromboplastin time. The authors observed that fibrinogen can increase in the early stages of severe disease but decline in the later stages. This could explain why cerebrovascular disease is prevalent in severely ill patients.

The investigators noticed a correlation in increases of alanine aminotransferase in COVID-19 patients, as well as several myocardial injury indexes such as aspartate aminotransferase (AST), creatine kinase, and lactate dehydrogenase. “Several significant differences were noted between severe and non-severe patients, especially higher values of AST,” wrote the authors.

This was also true of some inflammatory biomarkers. Raised CRP concentrations appeared in more than 57% of the patients studied. “CRP is a good predictor of adverse consequences and related to inflammation of tissues and organs,” observed the authors. Higher serum hypersensitive CRP in particular can signal poor outcomes in patients or predict mortality risk in severely ill patients. 

In patients with severe disease, the investigators also found lower levels of CD4 and CD8 and higher levels of inflammatory cytokines (IL-1β, IL-6, IL-10). CD3+T cells, IP-10, MCP-3, and IL-1ra were other lab indexes associated with severity and progression of disease.

“Overall, close monitoring of the T lymphocyte subsets and cytokines might provide valuable information on the patient’s condition change during the treatment process,” suggested the authors.