Lung function, measured by forced expiration, is normal in infants with CF at the time of diagnosis by newborn screening but is diminished in older infants. These findings suggest that in CF the optimal timing of therapeutic interventions aimed at preserving lung function may be within the first 6 months of life.

BackgroundIn school-aged children with cystic fibrosis (CF) structural lung damage assessed using chest CT is associated with abnormal ventilation distribution. The primary objective of this analysis was to determine the relationships between ventilation distribution outcomes and the presence and extent of structural damage as assessed by chest CT in infants and young children with CF.MethodsData of infants and young children with CF diagnosed following newborn screening consecutively reviewed between August 2005 and December 2009 were analysed. Ventilation distribution (lung clearance index and the first and second moment ratios [LCI, M1/M0 and M2/M0, respectively]), chest CT and airway pathology from bronchoalveolar lavage were determined at diagnosis and then annually. The chest CT scans were evaluated for the presence or absence of bronchiectasis and air trapping.ResultsMatched lung function, chest CT and pathology outcomes were available in 49 infants (31 male) with bronchiectasis and air trapping present in 13 (27%) and 24 (49%) infants, respectively. The presence of bronchiectasis or air trapping was associated with increased M2/M0 but not LCI or M1/M0. There was a weak, but statistically significant association between the extent of air trapping and all ventilation distribution outcomes.ConclusionThese findings suggest that in early CF lung disease there are weak associations between ventilation distribution and lung damage from chest CT. These finding are in contrast to those reported in older children. These findings suggest that assessments of LCI could not be used to replace a chest CT scan for the assessment of structural lung disease in the first two years of life. Further research in which both MBW and chest CT outcomes are obtained is required to assess the role of ventilation distribution in tracking the progression of lung damage in infants with CF.

1 The final equations provided age-, height-, sex-, and ethnic-specific predicted values and lower limits of normal for spirometry. The predicted equations for Caucasians were derived from 55 428 individuals and represent the largest 'all-age' spirometry reference values published to date. The methodological approach used by the Task Force is identical to that previously used to develop the Stanojevic et al. 'all-age' spirometry reference equations for Caucasians, 2 which we have recently shown to be appropriate for contemporary Australasian subjects. 3 The aim of this analysis was to ascertain how well the new European Respiratory Society GLI 2012 reference ranges fit contemporary Australasian spirometric data. Spirometry outcomes from 2066 Caucasian subjects aged 4-80 years (55% male) collected from 14 centres across Australia and New Zealand were included.3 Height-, age-and gender-specific Z-scores for forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), forced expiratory flows between 25% and 75% of FVC (FEF25-75) and FEV1/FVC were calculated for GLI 2012 equations using custom-made software. 4 We defined the minimum physiologically relevant difference to be 0.5 Z-scores, equating to a difference of~6% predicted.Mean (SD) Z-scores for the contemporary Australasian data were 0.23 (1.00) for FEV1, 0.23 (1.00) for FVC, -0.03 (0.87) for FEV1/FVC and 0.07 (0.95) for FEF25-75, all of which were well within range considered to be physiologically irrelevant. The mean Z-score differences equated to absolute and percent predicted differences of 89 mL and 3%, respectively, for FEV1, 117 mL and 3.2% for FVC, 127 mL/s, and 5.9% for FEF25-75 and a difference in FEV1/FVC of -0.49%. Although there were some weak, albeit statistically significant, associations between the spirometry Z-scores and age, height and sex or a combination of