1 Institute of Health Informatics Research, St Bartholomew's Hospital, Barts Heart Centre, Barts Health NHS Trust, West Smithfield, EC1A 7BE London, UK.
2 Institute of Health Informatics, University College of London, London, UK.
3 Epidemiology and Statistics Analysis Unit, Research Centre, Centro Hospitalar de Lisboa Central, EPE, Lisbon, Portugal.
4 Hospital de Santa Cruz, Centro Hospitalar Lisboa Ocidental, Carnaxide, Portugal.