The long-ter
m success of lung transplantation is challenged by the develop
ment of chronic lung allograft dysfunction (CLAD) and its distinct subtypes of bronchiolitis obliterans syndro
me (BOS) and restrictive allograft syndro
me (RAS). However, the current diagnostic criteria for CLAD subtypes rely on total lung capacity (TLC), which is not always
measured during routine post-transplant assess
ment. Our ai
m was to investigate the utility of low-dose 3-di
mensional co
mputed to
mography (CT) lung volu
metry for differentiating RAS fro
m BOS.
Methods
This study was a retrospective evaluation of 63 patients who had developed CLAD after bilateral lung or heart‒lung transplantation between 2006 and 2011, including 44 BOS and 19 RAS cases. Median post-transplant follow-up was 65 months in BOS and 27 months in RAS. The median interval between baseline and the disease-onset time-point for CT volumetry was 11 months in both BOS and RAS. Chronologic changes and diagnostic accuracy of CT lung volume (measured as percent of baseline) were investigated.
Results
RAS showed a significant decrease in CT lung volume at disease onset compared with baseline (mean 3,916 ml vs 3,055 ml when excluding opacities, m>pm> < 0.0001), whereas BOS showed no significant post-transplant change (mean 4,318 ml vs 4,396 ml, m>pm> = 0.214). The area under the receiver operating characteristic curve of CT lung volume for differentiating RAS from BOS was 0.959 (95% confidence interval 0.912 to 1.01, m>pm> < 0.0001) and the calculated accuracy was 0.938 at a threshold of 85%.
Conclusion
In bilateral lung or heart‒lung transplant patients with CLAD, low-dose CT volumetry is a useful tool to differentiate patients who develop RAS from those who develop BOS.