Chronic lung allograft dysfunction subtype analysis by computed tomography volumetry

Chronic lung allograft dysfunction (CLAD) limits long-term survival after lung transplantation. Of the two subtypes, restrictive allograft syndrome (RAS) is characterized by a larger lung volume decrease and worse prognosis than bronchiolitis obliterans syndrome (BOS). We used computed tomography (CT) volumetry to classify CLAD subtypes and determined their clinical impact.

Adult primary lung transplants performed 2003-2015 (n = 167) were retrospectively evaluated for CLAD and subclassified with CT volumetry. Lung volume decrease of < 15% from baseline resulted in BOS_CT-vol and ≥15% resulted in RAS_CT-vol diagnosis. Clinical impact of CLAD subtypes was defined, and the prognostic value of different lung function, radiological, and lung volume parameters present at the time of CLAD diagnosis were compared.

CLAD affected 43% of patients and was classified with CT volumetry as BOS_CT-vol in 89% and RAS_CT-vol in 11%. Median graft survival estimate in RAS_CT-vol was significantly decreased compared to BOS_CT-vol (1.6 vs. 9.7 years, P = .038). At CLAD onset, RAS_CT-vol diagnosis (P = .05), increased lung density (P = .007), and more severe FEV1 (P = .004) decline from baseline, increased graft loss risk in multivariate analysis.

CT volumetry serves to identify lung transplant patients with a poor clinical outcome but should be validated in prospective trials.