The influence of pulmonary infection on lung function in infants with cystic fibrosis

Previously we have shown that lower airway infection and inflammation are common in infants with cystic fibrosis (CF) diagnosed by neonatal screening. To explore the relationship between infection, inflammation and lung function we conducted a preliminary cross-sectional study in CF infants undergoing annual bronchoalveolar lavage (BAL) as part of a larger study of CF lung disease. Methods: 18 children with CF diagnosed on neoaatal screening, median age 22 (range 1-36) months, had BAL and lung fujictjon testing under general anaesthesia. Forced expiratory volume in half a second (FEVo.s) was determined using the raised volume rapid thoracic compression technique. A colony count greater than or equal to 10⁵ CFU/ml BAL fluid and/or a differential neutrophil count above 50% was considered positive for airway infection/inflammation. A control group without lung disease (n=6, median age 11 (range 5-32) months) had lung function testing as described under anaesthesia prior to minor elective surgery. Results: 7 (39%) of the 18 children with CF had respiratory symptoms and 3 (17%) were receiving oral antibiotics at the time of BAL. 8/18 children had positive BAL results by the above criteria, 50% of whom were symptomatic. Mean FEV0.5 (95%CI) adjusted by analysis of covariance for height for those with and without positive BAL findings was 238 (187,288) and 258 (211,300) respectively. The mean FEVos for the control group was 293.6 (95%CI 237,350). The difference between the three groups was not significant (p=0.36). Conclusion: Preliminary results show poorer lung function in infants and young children who have evidence of infection and/or inflammation on BAL, but this did not achieve statistical significance. More data is needed to determine whether infants with infection have reduced lung function and whether this is related to the presence of airway inflammation.