Analysis of the associations between lung function and clinical features in preschool children with cystic fibrosis.

OBJECTIVE: To analyze cross-sectional and longitudinal associations between lung function measures and clinical features in a cohort of preschool children with cystic fibrosis (CF). METHODS: Longitudinal eight-center observational study of children with CF aged 36-60 months at enrollment, who underwent semiannual pulmonary function tests (PFTs) for up to 2 years consisting of spirometry (all 8 sites), forced oscillometry (FO, 5 sites), and measures of thoracoabdominal asynchrony using respiratory inductive plethysmography (IP, 5 sites). RESULTS: Ninety-three subjects were enrolled; 181 acceptable spirometry measurements from 71 subjects, 128 FO from 47 subjects, and 142 IP from 50 subjects were available for analysis. Cross sectional analyses did not detect an association between any PFT parameter at enrollment and Pseudomonas aeruginosa (Pa) status, CF gene mutation class, Wisconsin cough score, Shwachman score, environmental tobacco smoke exposure, family history of asthma, or nutritional indices. In longitudinal analyses, Pa infection within 6 months preceding enrollment was associated with a significantly greater rate of decline in z-scores for forced expiratory flow between 25 and 75% of forced vital capacity (FEF(25-75) ) (-1.3 vs. -0.4 Z scores/year, P = 0.024) and greater thoracoabdominal asynchrony measured by IP (mean phase angle difference 4.6°, P = 0.004). No other significant longitudinal associations were observed. CONCLUSIONS: Prior Pa infection is associated with a greater rate of decline in FEF(25-75) z-score and mild thoracoabdominal asynchrony in preschool children with CF. In this multicenter US study, significant associations between other lung function measures and clinical features were not detected.