Table 3 Classification of patients based on sputum microbiological results

1

Occasional

≥ 1 isolation in a year

Chronic colonization is defined by the isolation of bacteria in sputum culture on 2 or more occasions, 3 months apart, within 1 year

2

Chronic previously

Chronic in preceding 5 years but not last 2 years

3

Chronic currently

Current, and chronic in last 2 years prior to recruitment