Patients' characteristics
| Parameter | Infants | BAL-earlyƒ | BAL-laterƒ |
| Total | 17 | 13 | 12 |
| Sex male | 8 (47) | 7 (54) | 4 (33) |
| CFTR mutation | |||
| Severe: mostly F508del/F508del# | 15 (88) | 11 (85) | 11 (92) |
| Milder: R334W - c1132 C>T | 1 (6) | 1 (8) | 1 (8) |
| Mild: F508del/R117H | 1 (6) | 1 (8) | 0 (0) |
| Elective BAL¶ | 13 (100) | 12 (100) | |
| Respiratory symptoms during BAL+ | 2 (15) | 2 (17) | |
| (Prophylactic) antibiotic use in previous month§ | 8 (62) | 11 (92) | |
| Age months mean (range) | 4.6 (3–8) | 12.4 (9–13) | |
| Weight kg | 6 (5–9) | 10 (9–11) | |
| Height cm | 63 (57–73) | 76 (72–84) |
Data are presented as n (%), unless otherwise indicated. BAL: bronchoalveolar lavage; CFTR: cystic fibrosis transmembrane conductance regulator. #: F508del/F508del (n=10), F508del/y1092X (n=1), F508del/2183AA>G (n=1), 1717–1G>A/2183AA>G (n=1), DF508/G461R, 1513>A (n=1), F508del/N1303K (n=1); ¶: according to a Dutch clinical surveillance protocol; +: patient's respiratory status (presence of cough, rhinorrhoea or shortness of breath) was defined as asymptomatic or symptomatic; §: by protocol, patients on antibiotics prophylaxis (mostly trimethoprim-sulfamethoxazole or amoxicillin) were asked to stop antibiotic prophylaxis for 3 days preceding the BAL procedure; ƒ: number of BAL procedures.