LAUSR

RATIONALE Lung Clearance index (LCI) has good intra-visit repeatability with better sensitivity in detecting lung disease on CT scan compared to Forced Expiratory Volume in 1 second (FEV1) in adults with bronchiectasis. Alternative multiple breath washout (MBW) parameters have not been systematically studied in bronchiectasis. OBJECTIVES To determine the validity, repeatability, sensitivity, specificity and feasibility of standard LCI (LCI2.5), shortened LCI (LCI5.0), ScondVT and SacinVT in a cross-sectional observational cohort of adults with bronchiectasis. METHODS Cross-sectional MBN2W data (Exhalyzer® D) from 132 patients with bronchiectasis across 5 UK centres (Bronch-UK Clinimetrics study) and 88 healthy controls were analysed. RESULTS Within test repeatability (mean CV%) was <5% for both LCI2.5 and LCI5.0 in patients with bronchiectasis and there was no difference in mean CV% in LCI2.5 and LCI5.0 in patients with bronchiectasis compared to healthy volunteers. Moderate strength correlations were seen between FEV1 and LCI2.5 (r=-0.54), LCI5.0 (r=-0.53), ScondVT (r=-0.35) and SacinVT z-scores (r=-0.38). The proportion of subjects with abnormal MBW (>2 z-score) but normal FEV1 (<-2 z-score) was 42% (LCI2.5) and 36% (LCI5.0). Overall results from the receiver operator characteristic curve (AUCROC) indicated that LCI2.5 had greatest combined sensitivity and specificity to discriminate between bronchiectasis and control subjects, followed by LCI5.0, FEV1 and ScondVT z-scores. There was a 57% time saving with LCI5.0. CONCLUSIONS LCI2.5 and LCI5.0 had good within test repeatability and superior sensitivity compared with spirometry measures, in differentiating between health and bronchiectasis disease. LCI5.0 is shorter and more feasible than LCI2.5. Clinical trial registered with ClinicalTrials.gov (NCT02468271).