1 Clinical Epidemiology and Medical Statistics Unit, Dept of Biomedical Sciences, University of Sassari - Research, Medical Education and Professional Development Unit, AOU Sassari, Italy.
2 Faculty of Medical and Human Sciences, University of Manchester, Manchester, UK Dept of Respiratory Medicine, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK mark.woodhead@cmft.nhs.uk.