Impaired performance of SARS-CoV-2 antigen-detecting rapid diagnostic tests at elevated and low temperatures

Abstract

\n Rapid antigen-detecting tests (Ag-RDTs) can complement molecular diagnostics for COVID-19. The recommended temperature for storage of SARS-CoV-2 Ag-RDTs ranges between 2-30\u2009°C. In the global South, mean temperatures can exceed 30\u2009°C. In the global North, Ag-RDTs are often used in external testing facilities at low ambient temperatures.\n We assessed analytical sensitivity and specificity of eleven commercially-available SARS-CoV-2 Ag-RDTs using different storage and operational temperatures, including short- or long-term storage and operation at recommended temperatures or at either 2-4\u2009°C or at 37\u2009°C. The limits of detection of SARS-CoV-2 Ag-RDTs under recommended conditions ranged from 1.0\u2009×\u2009106-5.5\u2009×\u2009107 genome copies/ml of infectious SARS-CoV-2 cell culture supernatant. Despite long-term storage at recommended conditions, 10\u2009minutes pre-incubation of Ag-RDTs and testing at 37\u2009°C resulted in about ten-fold reduced sensitivity for five out of 11 SARS-CoV-2 Ag-RDTs, including both Ag-RDTs currently listed for emergency use by the World Health Organization. After 3 weeks of storage at 37\u2009°C, eight of the 11 SARS-CoV-2 Ag-RDTs exhibited about ten-fold reduced sensitivity. Specificity of SARS-CoV-2 Ag-RDTs using cell culture supernatant from common respiratory viruses was not affected by storage and testing at 37\u2009°C, whereas false-positive results occurred at outside temperatures of 2-4\u2009°C for two out of six tested Ag-RDTs.\n In summary, elevated temperatures impair sensitivity, whereas low temperatures impair specificity of SARS-CoV-2 Ag-RDTs. Consequences may include false-negative test results at clinically relevant virus concentrations compatible with inter-individual transmission and false-positive results entailing unwarranted quarantine assignments. Storage and operation of SARS-CoV-2 Ag-RDTs at recommended conditions is essential for successful usage during the pandemic.\n