1. Discipline of General Practice, School of Medicine, University of Queensland, Brisbane, Queensland, Australia; and Tintenbar Medical Centre, 12 George Street, Tintenbar, New South Wales 2478, Australia;
2. Discipline of General Practice, School of Medicine, University of Queensland, Ipswich, Queensland, Australia
3. Research Unit, Tintenbar Medical Centre, Tintenbar, New South Wales, Australia
4. Discipline of General Practice, School of Medicine, University of Queensland, Brisbane, Queensland, Australia