Serial induced sputum sampling methodologies and results
| Parameter | Induced sputum number | ||
| 1 | 2 | 3 | |
| Microbiological results | |||
| Positive smear | 12 (6%) | 10 (5%) | 7 (4%) |
| Positive culture# | 160 (80%) | 163 (82%) | 142 (71%) |
| Colony count | 20 (3–100) | 20 (2–100) | 18 (2–100) |
| Induction methodology | |||
| Bronchodilator pre-treatment¶ | 34 (17%) | 24 (12%) | 19 (10%) |
| Airway clearance device+ | 198 (99%) | 158 (79%) | 160 (80%) |
| Hypertonic saline concentration | |||
| 3% | 10 (5%) | 6 (3%) | 8 (4%) |
| 7% | 131 (66%) | 126 (63%) | 116 (58%) |
| 10% | 59 (30%) | 68 (34%) | 76 (38%) |
| Incremental detection yields and selected sub-group comparisons | |||
| All patients | 160 (80%) | 27 (14%) | 13 (6%) |
| Single species (n=173) | 135 (78%) | 25 (14%) | 13 (8%) |
| Pulmonary cavitation§ | |||
| Present (n=51) | 47 (92%) | 4 (8%) | N/A |
| Absent (n=149) | 113 (76%) | 23 (15%) | 13 (9%) |
| Current treatment | |||
| Present (n=57) | 45 (79%) | 8 (14%) | 4 (7%) |
| Absent (n=143) | 115 (80%) | 19 (13%) | 9 (6%) |
| Inhaled corticosteroidsƒ | |||
| Present (n=44) | 31 (70%) | 7 (16%) | 6 (14%) |
| Absent (n=156) | 129 (83%) | 20 (13%) | 7 (4%) |
Data are presented as n (%) or median (interquartile range). #: rates of culture positivity differed with sputum number (p=0.03); ¶: there was a trend towards differing of rates of bronchodilator pre-treatment with sputum number (p=0.08); +: rates of airway clearance device (Aerobika or vest) use during induction differed with sputum number (p<0.001); §: detection yields differed with present/absent cavitation (p=0.02); ƒ: there was a trend towards differing of detection yields with present/absent inhaled corticosteroid use (p=0.07).