False-negative RT-PCR for COVID-19 and a diagnostic risk score: a retrospective cohort study among patients admitted to hospital oleh Ashley Whittington, Ankur Gupta-Wright, Colin Kenneth Macleod, Sarah Ann Filson, Tumena Corrah, Victoria Parris, Miriam Harris, Rachel Tennant, Nidhi Vaid, Junko Takata, Sai Duraisingham, Nemi Gandy, Harmeet Chana, Alastair McGregor, Padmasayee Papineni