Predictors and Outcome of Low Initial Forced Expiratory Volume in 1 Second Measurement in Children with Cystic Fibrosis

Objective To identify the characteristics of children with cystic fibrosis with low initial forced expiratory volume in 1 second (FEV1 ) % predicted and to investigate their outcome. Study design Patients were categorized into low or high initial FEV1 groups using cluster analysis. Comparisons of the demographic and clinical data were performed between the 2 groups. Results From 122 children, 21 clustered into the low and 101 into the high FEV1 group. The mean FEV1 was 69% ± 12% predicted for the low and 95% ± 12% predicted for the high FEV1 group ( P < .001). The low FEV1 group had lower body mass index percentiles ( P = .003), were hospitalized more frequently ( P = .001), and had been on dornase alfa longer ( P = .006). Low FEV1 group had more patients with positive cultures for Pseudomonas aeruginosa ( P = .002) and Stenotrophomonas maltophilia ( P < .001) and had more total number of cultures positive for mucoid P aeruginosa ( P = .009) and methicillin resistant Staphylococcus aureus + P aeruginosa ( P = .005). The low FEV1 group continued to have low FEV1 measurements, their FEV1 declined slower, required more hospitalizations per year ( P = .01), and had more cultures for mucoid ( P = .003) and nonmucoid P aeruginosa ( P = .02) ± methicillin resistant S aureus ( P = .002) in comparison with the high FEV1 group. Poor adherence was associated with lower initial FEV1 values in females, and early, rapid decline of FEV1 in males. Conclusions Some children with cystic fibrosis may present with poor lung function early in life and continue to have subnormal lung function associated with reduced body mass index, more frequent hospitalization, and higher rates of infection. Such children may benefit from careful evaluation and close follow-up.