Association of lung function, chest radiographs and clinical features in infants with cystic fibrosis

The optimal strategy for monitoring cystic fibrosislung disease in infancy remains unclear. Our objective was to describe longitudinal associations between infant pulmonary function tests, chest radiographscores and other characteristics. Cystic fibrosispatients aged ≤24 months were enrolled in a 10-centre study evaluating infant pulmonary function testsfour times over a year. Chest radiographs∼1 year apart were scored using the Wisconsin and Brasfield systems. Associations of infant pulmonary function testswith clinical characteristics were evaluated with mixed effects models. The 100 participants contributed 246 acceptable flow/volume (forced expiratory volume in 0.5 s (FEV 0.5 ) and forced expiratory flow at 75% of the forced vital capacity (FEF 75% )), 303 functional residual capacitymeasurements and 171 chest radiographs. Both Brasfield and Wisconsin chest radiographscores worsened significantly over the 1-year interval. Worse Wisconsin chest radiographscores and Staphylococcus aureus were both associated with hyperinflation(significantly increased functional residual capacity), but not with diminished FEV 0.5 or FEF 75% . Parent-reported cough was associated with significantly diminished forced expiratory flow at 75% but not with hyperinflation. In this infant cohort in whom we previously reported worsening in average lung function, chest radiographscores also worsened over a year. The significant associations detected between both Wisconsin chest radiographscore and S. aureus and hyperinflation, as well as between cough and diminished flows, reinforce the ability of infant pulmonary function testsand chest radiographsto detect early cystic fibrosislung disease.