Background: Sputum rheology measures the visco-elastic and mechanical properties of airway secretions. Parameters include the critical stress that quantifies the force needed to make the mucus flow and thought to be linked to the capacity for airway clearance. Little is known about the reproducibility of the method across different specialist centres.

Aim: To compare the critical stress and other standard rheological parameters observed in non-cystic fibrosis bronchiectasis (NCFB) and severe asthma (SA) across two clinical centres.

Methods: Sputum was collected from patients with NCFB and SA in Manchester (MCR) UK & Montpellier (MP) France. Both specialist centres used the same rheometer (Rheonova) providing 4 values (viscoelasticity , damping ratio, critical strain & stress), that were compared across cohorts and centres using T-tests.

Results: Rheology results were obtained for NCFB (n=16 & 76) and SA (n=20 & 27) in MCR & MP respectively. The critical stress was lower in NCFB (Log transformed mean 1.44(SD 0.39) compared to SA  (1.70(0.57) p=0.007) but were of similar magnitude across the centres (NCFB p=0.79, SA p=0.70 (Figure)).

Conclusions: Critical stress, believed to measure the force needed to make sputum flow in the airways is a reproducible rheological parameter across specialist centres in obstructive diseases with potential clinical management applications.