Context: An abundance of clinical reports focused on specific laboratory parameters have been reported on COVID-19, but a systematic analysis synthesizing these findings has not been performed. Objective: To review and summarize the current available literature on the predictive role of various biomarkers in COVID-19 patients. Data Sources: A literature search was performed using databases including PubMed, medRxiv, and bioRxiv. A total of 72 papers were reviewed including 54 peer reviewed papers and 18 non-peer reviewed preprints. Conclusions: While non-specific, acute phase reactants including CRP, ferritin, SAA, and procalcitonin were reported as sensitive markers of acute COVID-19 disease. Significantly elevated WBC count, marked lymphopenia, decreased CD3, CD4 or CD8 T-lymphocyte counts, high neutrophil count, thrombocytopenia, and markedly elevated inflammatory biomarkers were associated with severe disease and the risk of developing sepsis with rapid progression. Trends observed by serial laboratory measurements during hospitalization including progressive decrease of lymphocyte count, thrombocytopenia, elevated CRP, procalcitonin, increased liver enzymes, decreased renal function, and coagulation derangements were more common in critically ill patient groups and associated with a high incidence of clinical complications. Elevated IL-6 level and markedly increased SAA were most often reported in severely and critically ill patients. Indicators of systemic inflammation such as neutrophil-lymphocyte ratio (NLR), systemic immune-inflammation (SII) index or COVID-19 Severity Score may be utilized to predict disease severity, outcome, and mortality. Interpretation of the data reported in the studies reviewed here is limited due to study design (mostly retrospective), limited sample size, and a lack of defined clinical criteria.

Objectives To examine and summarize the current literature on serologic methods for the detection of antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Methods A literature review was performed using searches in databases including PubMed, medRxiv, and bioRxiv. Thirty-two peer-reviewed papers and 23 preprints were examined. Results The studies included lateral flow immunoassay, enzyme-linked immunosorbent assay, chemiluminescence immunoassay, and neutralizing antibody assays. The use of all major SARS-CoV-2 antigens was demonstrated to have diagnostic value. Assays measuring total antibody reactivity had the highest sensitivity. In addition, all the methods provided opportunities to characterize the humoral immune response by isotype. The combined use of IgM and IgG detection resulted in a higher sensitivity than that observed when detecting either isotype alone. Although IgA was rarely studied, it was also demonstrated to be a sensitive marker of infection, and levels correlated with disease severity and neutralizing activity. Conclusions The use of serologic testing, in conjunction with reverse transcription polymerase chain reaction testing, was demonstrated to significantly increase the sensitivity of detection of patients infected with SARS-CoV-2. There was conflicting evidence regarding whether antibody titers correlated with clinical severity. However, preliminary investigations indicated some immunoassays may be a surrogate for the prediction of neutralizing antibody titers and the selection of recovered patients for convalescent serum donation.

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