Non-invasive detection of multinucleated giant cells in the conjunctiva of patients with sarcoidosis by in-vivo confocal microscopy

Aim: To explore the use of in-vivo confocal microscopy (IVCM) as a potential non-invasive adjunctive tool for diagnosing sarcoidosis. Methods: Conjunctivae were imaged using confocal microscopy in 10 patients with sarcoidosis and 27 control subjects. We utilized the ASL-1000 Scanning Confocal Microscope (Advanced Scanning Ltd., New Orleans, LA) and the Confoscan 3 (Nidek Co. Ltd., Gamagori, Japan). Two masked observers reviewed the in-vivo confocal images of the conjunctivae in these subjects. One masked observer was experienced in reviewing confocal images. The most striking and obvious feature seen in granulomatous inflammation on confocal microscopy is the presence of multinucleated giant cells (MGCs). Results: Unmasked observation of the scans revealed MGCs in six of the 10 sarcoid patients and no MGCs in the controls. One experienced masked observer found MGCs in five of the 10 patients with sarcoidosis and had no false-positive results (Fisher's exact test, p = 0.001; specificity = 1; sensitivity = 50% for the diagnosis of sarcoidosis and 83% compared to the unmasked observer). The second less-experienced masked observer detected MGCs in three of the 10 patients and three of the 27 controls (11.1% of the controls) (p = 0.186; specificity = 0.89; sensitivity = 30% of all patients with sarcoidosis and 50% compared to the unmasked observer). Conclusions: The utilization of IVCM to visualize the basic histology and pathology in sarcoidosis of the conjunctiva is novel. Initial results indicate that trained observers can detect MGCs in granulomatous inflammation. The ASL-1000 microscope tends to have better resolution and deeper penetration of the conjunctiva compared with the Confoscan 3.