We report of two cases of progressed COVID-19 with negative PCR tests from nasopharyngeal swabs, in whom diagnosis was made by different antibody assays, including a lateral flow rapid test and multiple commercial ELISAs, finally confirmed by comprehensive serological assays. These cases highlight that commercial ELISAs and even rapid tests might significantly aid the diagnosis of COVID-19, particularly, if a combination of serological assays is used with a specific clinical question, in severely ill patients after seroconversion and when comprehensive serological methods are used for confirmation.
Keywords: Antibodies; Coronavirus; Immunoassay; PCR negative; Rapid test; SARS.