[1] Aberdeen Royal Infirm, Chest Clin C, StR Resp Med, Aberdeen, Scotland
[2] Aberdeen Royal Infirm, Chest Clin C, Aberdeen, Scotland
[3] Aberdeen Royal Infirm, Pathol Dept, Aberdeen, Scotland
[4] Univ Glasgow, Inst Infect Inflammat & Immun, Resp Med, Glasgow, Lanark, Scotland