Background
Non cystic fibrosis, non primary ciliary dyskinesia bronchiectasis (nCFnPCD-BE) results in significant morbidity with few evidence-based treatments.

Objective
assessments are required to assess severity and evaluate treatment. Lung clearance index (LCI) measures ventilation inhomogeneity and is a sensitive test of disease in CF; its use in nCFnPCD-BE is unclear.

Methods
A systematic review of LCI in nCFnPCD-BE was performed using standard methodology (protocol registered on PROSPERO, University of York).

Results
Of 276 records identified, 12 articles, describing 519 adult and paediatric patients in cross-sectional studies were included, addressing several domains.

1: What is the utility of LCI in detecting disease and severity?

LCI detected disease in adults, differentiating bronchiectasis from controls (AUC 0.90 to 0.96) and mild from moderate/severe bronchiectasis on CT (AUC 0.73).

2: Does LCI correlate with spirometry and imaging?

LCI correlated with spirometry in adult (r = −0.37 to −0.61) and paediatric (r = −0.6) groups, signs of bronchiectasis on CT, and CT scoring systems (modified Reiff).

3: Does LCI relate to subjective scores of severity?

In adults, LCI correlated with St. George's Respiratory Questionnaire (r = 0.18) and Bronchiectasis Severity Index (r = 0.45).

4: Does LCI identify response to intervention?

LCI did not change in studies examining LCI pre-post intervention (adults treated for exacerbation and undergoing physiotherapy).

Overall study quality was variable.

Conclusion
Contrary to data in CF, the review did not identify good quality studies defining the role of LCI in children with bronchiectasis. In adults, LCI was a sensitive measure of disease severity and correlated with clinical assessment tools.