Background Delaying onset and early recognition of CLAD are clinically relevant strategic targets in lung transplantation. Flow volume (FV) curves provide a simple easy visual indicator of early/persistent allograft injury and scalloping on FV loop in particular is a marker of small airway obstruction which is characteristic of CLAD-BOS.

Aims and objectives To study if early scalloping on FV loop at 3 months post-transplant can predict onset of CLAD-BOS at 1 year post transplant and influence frequency of acute cellular rejection (ACR) or survival.

Methodology This is a non-interventional retrospective study involving all patients who underwent bilateral lung transplantation from 2012-2015 at Freeman Hospital, Newcastle Upon Tyne, UK. Serial post-transplant monitoring data were reviewed. Spirometry at 3 months post lung transplant, FV loop, incidence of ACR, BOS and long term survival post transplant were recorded and analyzed.

Results 156 subjects-93 males (59.6%) who underwent bilateral lung transplantation were included. 42 (27%) subjects demonstrated scalloping of FV loop at 3 months. Subjects with scalloping of FV loop have significant higher incidence of BOS at 1 & 2 year (16.7% & 26.2%) compared to those without scalloping (5.3% & 8%), p=0.023 & 0.002 respectively. Kaplan-Meier survival analysis estimates shorter median survival in subjects with scalloping (7.56 years versus 8.9 years), p=0.222. There is no significant correlation between scalloping of FV loop and number of ACR?s at 1 year.

Conclusions Early detection of scalloping on FV loop is clinically relevant and increases incidence of CLAD-BOS.