Clinical laboratory evaluation of COVID-19

•Nucleic acid tests can serve as the pathogenic evidence for the diagnosis of COVID-19.•Specific antibodies of SARS-CoV-2 (IgG, IgM, and IgA) are the effective complement for false-negative detection of SARS-CoV-2 nucleic acid in clinically suspected cases.•Antigen tests to identify SARS-CoV-2 infection are recommended in the early stages with high viral loads.•Dynamic detection of some biomarkers such as lymphocytes, LDH, AST, D-dimer, CRP, SAA, and IL-6 will be helpful as an early warning of serious diseases, especially in high-risk patients of severe and critical illness. COVID-19, caused by SARS-CoV-2, is a highly infectious disease, and clinical laboratory detection has played important roles in its diagnosis and in evaluating progression of the disease. Nucleic acid amplification testing or gene sequencing can serve as pathogenic evidence of COVID-19 diagnosing for clinically suspected cases, and dynamic monitoring of specific antibodies (IgM, IgA, and IgG) is an effective complement for false-negative detection of SARS-CoV-2 nucleic acid. Antigen tests to identify SARS-CoV-2 are recommended in the first week of infection, which is associated with high viral loads. Additionally, many clinical laboratory indicators are abnormal as the disease evolves. For example, from moderate to severe and critical cases, leukocytes, neutrophils, and the neutrophil–lymphocyte ratio increase; conversely, lymphocytes decrease progressively but are over activated. LDH, AST, ALT, CK, high-sensitivity troponin I, and urea also increase progressively, and increased D-dimer is an indicator of severe disease and an independent risk factor for death. Severe infection leads to aggravation of inflammation. Inflammatory biomarkers and cytokines, such as CRP, SAA, ferritin, IL-6, and TNF-α, increase gradually. High-risk COVID-19 patients with severe disease, such as the elderly and those with underlying diseases (cardiovascular disease, diabetes, chronic respiratory disease, hypertension, obesity, and cancer), should be monitored dynamically, which will be helpful as an early warning of serious diseases.