Variation in lung function is associated with worse clinical outcomes in cystic fibrosis

OBJECTIVE: To determine whether the variation in lung function over one year is associated with worse clinical outcomes, as well as with a decline in lung function in the following years, in patients with cystic fibrosis (CF). METHODS: This was a retrospective study involving CF patients (4-19 years of age), evaluated over a three-year period. We evaluated demographic characteristics, chronic Pseudomonas aeruginosa infection, antibiotic use, hospitalization, six-minute walk distance (6MWD), and lung function. The inclusion criterion was having undergone pulmonary function testing at least three times in the first year and at least once in each of the next two years. RESULTS: We evaluated 35 CF patients. The variation in FEV(1) in the first year (ΔFEV(1)) was greater among those who, in the third year, showed reduced FEV(1), had a below-average 6MWD, or were hospitalized than among those with normal FEV(1), normal 6MWD, or no hospital admissions, in that same year (p < 0.05), although no such difference was found for antibiotic use in the third year. Subjects showing a ΔFEV(1) ≥ 10% also showed a greater decline in FEV(1) over the two subsequent years (p = 0.04). The ΔFEV(1) also showed an inverse correlation with absolute FEV(1) in the third year (r = −0.340, p = 0.04) and with the rate of FEV(1) decline (r = −0.52, p = 0.001). Linear regression identified ΔFEV(1) as a predictor of FEV(1) decline (coefficient of determination, 0.27). CONCLUSIONS: Significant variation in lung function over one year seems to be associated with a higher subsequent rate of FEV(1) decline and worse clinical outcomes in CF patients. Short-term ΔFEV(1) might prove useful as a predictor of CF progression in clinical practice.