The latest outbreak of pneumonia caused by SARS-CoV-2 presents a significant challenge to global public health and has a major impact on clinical microbiology laboratories. In some situations, such as patients in coma condition, the oropharyngeal or nasopharyngeal sampling is seldom feasible, and blood sampling could be an alternative. In the current article, a comprehensive literature search has been conducted for detecting coronavirus disease 2019 (COVID-19) using plasma or serum samples. To date, twenty-six studies have used SARS-CoV-2 nucleic acid in plasma or serum (RNAaemia) to diagnose COVID-19. The pros and cons are discussed in this article. While the detection of SARS-CoV-2 viral load in respiratory specimens is commonly used to diagnose COVID-19, detecting SARS-CoV-2 RNA in plasma or serum should not lose sight and it could be considered as an alternative diagnostic approach.