Minimal acute cellular rejection remains prevalent up to 2 years after lung transplantation: A retrospective analysis of 2697 transbronchial biopsies

Background. Acute cellular rejection (ACR) is the most consistently reported risk factor for the development of bronchiolitis obliterans syndrome, an important cause of late mortality after lung transplantation. This retrospective study comprised all transbronchial biopsies (TBB) obtained during the first 2 years after transplantation in a consecutive cohort of 299 patients transplanted 1996-2006 (n=2697). Methods. TBB were aligned to the closest TBB surveillance schedule. Results. Patients completed a mean of 6+/-2 (median 8) TBB schedules. The proportion of patients demonstrating ACR (>= A2) decreased with increasing time from transplantation from 43% at 2 weeks to 27% at 6 months, and 13% and 4% at I and 2 years, respectively (trend test, P<0.0001). There was a significant trend between increased previous occurrence of ACR and increasing subsequent risk of A 2 from 1, 3, and 12 months after transplantation (P<0.0001, P=0.0005, and P=0.001, respectively). Multivariate analyses identified interleukin-2-receptor induction with daclizumab versus antithymocyte globulin was independently associated with more frequent/severe ACR (P<0.0001). Conclusions. Minimal ACR remains prevalent up to 2 years after lung transplantation. Previous occurrence of ACR was associated with an increased risk of subsequent ACR.