In vivo probe-based confocal laser endomicroscopy in chronic interstitial lung diseases: Specific descriptors and correlation with chest CT

Background and objective: Probe-based confocal laser endomicroscopy (pCLE) enables in vivo microimaging of the distal lung, during bronchoscopy. This study aims at identifying pCLE descriptors of chronic interstitial lung diseases (ILD), their correlations with chest HRCT and assessing inter-observer agreement.

Methods: pCLE was performed in 21 healthy volunteers (HV) and 59 non-smoking ILD patients, including 19 patients with idiopathic pulmonary fibrosis (IPF) or asbestosis, 15 with connective tissue disease-associated ILD (CTD-ILD), 17 with sarcoidosis and 8 with hypersensitivity pneumonitis (HP). pCLE descriptors were identified in ILD on the basis of comparison with HV.

Results: Nine pCLE descriptors were more frequent in ILD compared to HV, with good inter-observer agreement, including fluorescent bronchiolar cells (sarcoidosis, CTD-ILD and HP), fluorescent alveolar cells (CTD-ILD and HP), small alveolar entrance rings (IPF or asbestosis and CTD-ILD), enlarged axial elastic fibres (IPF or asbestosis), septal fibres (IPF or asbestosis, CTD-ILD and HP), disorganized acinar network and rigid acinar network (IPF or asbestosis and CTD-ILD), dense elastic network (IPF or asbestosis) and alveolar fluorescent nodular structures (in sarcoidosis) (P < 0.01, Fisher's exact test, all comparisons). The distribution of nodules on computed tomography (CT) appeared to correlate with pCLE alveolar nodular structures, rigid acinar network and septal fibres, while reticulations were associated with septal fibres and disorganized or dense acinar network; ground-glass opacities on CT with small alveolar entrances, rigid elastic network and septal fibres; and honeycombing with septal fibres.

Conclusion: In the four groups of ILD studied, 9 pCLE descriptors are described, which appear specific and reproducible, and correlate with chest HRCT patterns.