Baseline characteristics | All | Cluster 1 Stable, near normal LCI | Cluster 2 Near normal LCI, increasing | Cluster 3 Abnormal LCI, stable/improving | Cluster 4 Abnormal LCI, increasing | P value |

n (%) | 81 | 58 (72) | 8 (10) | 7 (9) | 8 (10) | |

Age, mean (SD) | 15.5 (9.9) | 14.3 (8.2) | 13.8 (8.2) | 20.6 (20.5) | 21.6 (9.2) | 0.191 |

Age at diagnosis, mean (SD) | 4.4 (9.2) | 3.6 (6.9) | 3.2 (6.9) | 11.3 (22.4) | 5.76 (6.6) | 0.221 |

Baseline LCI, mean (SD) | 8.0 (1.7) | 7.3 (0.9) | 8.2 (1.4) | 10.0 (0.7) | 11.2 (1.5) | <0.001 |

FEV_{1} z-score, mean (SD) | −1.27 (1.30) | 0.99 (1.17) | −1.34 (1.04) | −1.35 (1.15) | −3.11 (1.16) | 0.003 |

FEF z-score, mean (SD) | −1.27 (1.45) | −0.99 (1.37) | −1.47 (1.30) | −1.03 (1.03) | −3.25 (0.94) | 0.0014 |

FVC z-score, mean (SD) | −0.68 (1.10) | −0.46 (0.97) | −0.59 (0.86) | −1.15 (1.05) | −1.92 (1.48) | 0.031 |

Total number of antibiotic courses for exacerbations/year, median (IQR) | 1.2 (0.7–2.2) | 1.2 (0.7–2.1) | 1.6 (1.0–3.1) | 1.1 (0.4–2.3) | 1.4 (0.8–4.4) | 0.517 |

Number of courses of intravenous antibiotics/year, median (IQR) | 0 (0–0.4) | 0 (0–0.4) | 0.3 (0–1.1) | 0 (0–0.5) | 0.4 (0–1.3) | 0.096 |

BMI (kg/m^{2}), mean (SD) | 19.5 (4.0) | 19.4 (3.9) | 18.6 (3.5) | 19.0 (4.9) | 21.7 (4.7) | 0.351 |

Phe508del homozygotes, n (%) | 41 (50.6) | 30 (51.7) | 4 (80.0) | 4 (57.1) | 3 (37.5) | 0.910 |

Male, n (%) | 45 (55.6) | 31 (53.5) | 3 (37.5) | 6 (85.7) | 5 (62.5) | 0.304 |

Pancreatic sufficient, n (%) | 23 (28.4) | 17 (29.3) | 1 (12.5) | 2 (28.6) | 3 (37.5) | 0.751 |

Pseudomonas aeruginosa status, n (%) | 18 (22.2) | 13 (22.4) | 2 (25.0) | 1 (14.3) | 2 (25.0) | 0.991 |

Chronic infection with Haemophilus influenzae, n (%) | 13 (16.5) | 11 (19.6) | 1 (12.5) | 0 (0) | 1 (12.5) | 0.811 |

Chronic infection with Aspergillus, n (%) | 14 (19.2) | 9 (16.7) | 1 (14.3) | 2 (33.3) | 2 (33.3) | 0.472 |

For continuous variables, the Kruskal-Wallis test was used to compare the means of the four groups without assuming normality and homogeneity of variances. For categorical data, Fisher-Freeman-Halton exact test was used.

Bold values indicate statistical significance.

BMI, body mass index; FEF, forced expiratory flow between 25% and 75% of FVC; FVC, forced vital capacity; LCI, lung clearance index.;