S67 Lung Clearance Index (lci) Is A Sensitive Predictor Of High Resolution Computed Tomography (hrct) Scores In Children With Non-cf Bronchiectasis

Introduction and objectives LCI is a sensitive predictor of early cystic fibrosis (CF) lung disease, and correlates with HRCT better than spirometry (Thorax. 2008;63:129–134). The same is true in adults with non-CF bronchiectasis (Am J Respir Crit Care Med. 2014;189:586–592.), but by contrast, in PCD there were no relationships between LCI, HRCT or spirometry (Am J Respir Crit Care Med. 2013;188:545–549). It is unclear whether these differences reflect primary versus secondary ciliary dyskinesia, or CFTR versus non-CFTR disease. We hypothesised that in children with non-CF bronchiectasis, relationships between spirometry, LCI and HRCT will be similar to those in CF children and non-CF bronchiectasis adults, rather than PCD patients. Methods 12 children with non-CF bronchiectasis performed LCI and spirometry and underwent thoracic HRCT. HRCT scans were scored quantitatively (Thorax. 2013;68:532–539). Results were compared with those from large CF (n = 125) and PCD (n = 38) cohorts. Results In non-CF bronchiectasis there was a correlation between first second forced expired volume (FEV1) and LCI (p = 0.009, r=-0.6), similar to that seen in CF (p < 0.0001, r=-0.6) but not in PCD (Figure). In non-CF bronchiectasis LCI was more significantly correlated with HRCT (extent and severity of bronchiectasis (p = 0.002, r = 0.8 and p = 0.01, r = 0.7 respectively), airway wall thickening (p = 0.01, r = 0.7) and air trapping (p = 0.0006, r = 0.8)) than was spirometry (only correlation with air trapping (p = 0.03, r=-0.6)). As shown previously, there were good correlations between HRCT and LCI in CF, but in PCD only air trapping correlated with LCI, and there were no correlations with FEV1. Conclusions LCI is a good marker of structural lung disease in children with non-CF bronchiectasis and is more sensitive to HRCT abnormalities than spirometry, similar to adults, and CF at all ages. This suggests the different relationships seen in PCD result from the effects of primary versus secondary ciliary dyskinesia rather than CFTR versus non-CFTR lung disease. LCI may be useful in monitoring children with non-CF bronchiectasis, but this needs to be confirmed longitudinally. The results illustrate the importance of not extrapolating between different airway diseases.