Acute lung allograft rejection: Diagnostic role of probe-based confocal laser endomicroscopy of the respiratory tract

Acute cellular rejection (AR) after lung transplantation may result in significant morbidity and mortality both on the short and long term. Transbronchial biopsy through flexible bronchoscopy is highly sensitive for the diagnosis of AR, but reproducibility of histopathologic interpretation is less convincing. Probe-based confocal laser endomicroscopy (pCLE), a novel imaging tool in the field of respiratory medicine, enables real-time imaging of the pulmonary acini.We performed 105 bronchoscopies in lung transplant recipients, combining both transbronchial biopsies and pCLE. We conducted an observational survey for pCLE findings in AR.Calculations for cellularity showed a median cell count (ACA) of 50 (IQR 18 to 120) cells per microscopic field for AR and 10 (IQR 0 to 15) cells per microscopic field for matched controls (p = 0.0004). Cellular autofluorescence in the AR group was 1,163 (± 157) units and 489 (± 101) units for the matched controls (p = 0.0009). Autofluorescent cells were present in 73% (± 10) of the recorded frames in the AR group and in only 42% (± 9) of the recorded frames in the control group (p = 0.03). Contingency analysis for the presence/absence of ACA in the AR group versus the control group showed a sensitivity of 0.93 and a specificity of 0.46 (relative risk = 6.5 [95% CI 0.94 to 44.8], p = 0.01). The consecutive application of 3 pCLE criteria resulted in a sensitivity of 0.93 and a specificity of 0.83 for detection of AR.Our observational survey suggests the existence of specific pCLE characteristics in patients with AR. Further efforts are necessary to validate these findings prospectively.