Introduction: Needle based confocal laser endomicroscopy (nCLE) allows real-time microscopic imaging at the needle tip. nCLE malignancy criteria are validated and used for bronchoscopic lung nodule detection. To date, nCLE granuloma criteria are not validated.

Aim: assess the accuracy, inter-observer agreement (IOA) and intra-observer reliability (IOR) of nCLE granuloma detection

Methods: In patients with suspected sarcoidosis, nCLE-imaging of mediastinal lymph nodes was performed during endoscopic ultrasound procedures, followed by needle aspiration. nCLE-videos were compared to final diagnoses  for granuloma criteria identification. Blinded raters, trained in nCLE granuloma criteria, validated nCLE videos of reactive and sarcoid lymph nodes. In patients with granulomatous lung nodules, bronchoscopic nCLE-imaging was performed.

Results: Five blinded raters evaluated 26 nCLE-videos of lymph nodes (n=15 sarcoid; n=11 reactive) of 19 patients twice (260 ratings). Granuloma criteria were recognized with 88.7% sensitivity and 87.3% specificity. The IOA (?=0.63, 95%CI 0.54-0.72) and IOR (?=0.70 ±0.06) were substantial. In 4 patients with granulomatous lung nodules similar nCLE criteria were observed.

Conclusion: nCLE imaging of lymph nodes and nodules is able to visualize granulomas in-vivo. Raters accurately and consistently recognized nCLE-granuloma criteria. nCLE can be used to recognize malignancy and granulomas in peripheral lung nodules