Given that the range of LCI and moment ratio values in those infants and young children with lung damage was within that of individuals without lung damage (Figure 3) it is evident that assessments of ventilation distribution in early life are unlikely to be Mdm2 useful as a screening tool to identify those infants with lung damage as has been suggested in studies in school aged children [15], [16], [18]. Another limiting factor of the present study was the use of a three-slice chest CT scan which may over or under-estimate the presence of bronchiectasis and structural lung disease [31]. In March 2007 the AREST CF collaboration commenced the use of low-dose volumetric chest CT scans.

The limited data from volumetric scans confirmed the complete overlap of values of LCI for those children with and without structural lung disease (data not shown) and suggest that the results reported here are not significantly influenced by the chest CT method used. Lum et al reported no associations between mode of diagnosis, clinical history of recent symptoms and LCI in infants diagnosed following clinical presentation [10]. In infants diagnosed with CF following NBS Belessis reported increased LCI in infants infected with Pseudomonas aeruginosa (n=7; LCI=7.66: 7.26�C8.48: median: inter-quartile range) when compared to infants infected with other organisms (n=40; LCI=7.03: 6.56�C7.41: p=0.007). The primary aim of this analysis was to investigate the relationship between structural lung damage and ventilation distribution outcomes and as such this analysis was not powered to assess the impact of infection or other potentially relevant clinical factors such as mutation type, nutritional status or presence of symptoms on ventilation distribution outcomes.

Further studies with larger number of infants with CF with a broader range of lung disease are required to investigate the impact of these clinical outcomes on ventilation distribution in infants and young children with CF. The London CF collaboration recently demonstrated that LCI measured between three and five years of age tracks through to school age suggesting that measurements of LCI in early life may assist in identifying the early onset of CF lung disease [13].

The associations reported here may represent the initial stages of the link between abnormal LCI and lung damage seen in older children and further longitudinal studies following the comparative evolution of LCI and lung damage until school-age are needed so as to provide further information on the early development of an abnormal LCI and its potential to predict AV-951 an abnormal chest CT in the early school years. In summary we report that the lung clearance index and moment ratios derived from the multiple breath washout technique cannot identify the presence of structural lung disease in infants and young children diagnosed with cystic fibrosis following newborn screening.