2 Biostatistics Unit, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.
3 FAST and Chronic Programmes, Alexandra Hospital, National University Health System, Singapore, Singapore.
4 Division of Respiratory & Critical Care Medicine, Department of Medicine, National University Hospital, National University Health System, Singapore, Singapore.
5 Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore; and.
6 Medical Affairs, Alexandra Hospital, Singapore, Singapore.