Needle-based confocal laser endomicroscopy for the diagnosis of pancreatic cystic lesions: an international external interobserver and intraobserver study

Background and Aims: EUS-guided needle-based confocal laser endomicroscopy (nCLE) characteristics of common types of pancreatic cystic lesions (PCLs) have been identified; however, surgical histopathology was available in a minority of cases. We sought to assess the performance characteristics of EUS nCLE for differentiating mucinous from non-mucinous PCLs in a larger series of patients with a definitive diagnosis. Methods: Six endosonographers (nCLE experience >30 cases each) blinded to all clinical data, reviewed nCLE images of PCLs from 29 patients with surgical (n=23) or clinical (n=6) correlation. After 2 weeks, the assessors reviewed the same images in a different sequence. A tutorial on available and novel nCLE image patterns was provided before each review. The performance characteristics of nCLE and the kappa statistic for interobserver agreement (IOA, 95% confidence interval [CI]), and intraobserver reliability (IOR, mean +/- standard deviation [SD]) for identification of nCLE image patterns were calculated. Landis and Koch interpretation of kappa values was used. Results: A total of 29 (16 mucinous PCLs, 13 non-mucinous PCLs) nCLE patient videos were reviewed. The overall sensitivity, specificity, and accuracy for the diagnosis of mucinous PCLs were 95%, 94%, and 95%, respectively. The IOA and IOR (mean +/- SD) were kappa =0.81 (almost perfect); 95% CI, 0.71-0.90; and kappa =0.86 +/- 0.11 (almost perfect), respectively. The overall specificity, sensitivity, and accuracy for the diagnosis of serous cystadenomas (SCAs) were 99%, 98%, and 98%, respectively. The IOA and IOR (mean +/- SD) for recognizing the characteristic image pattern of SCA were kappa = 0.83 (almost perfect); 95% CI, 0.73-0.92; and kappa = 0.85 +/- 0.11 (almost perfect), respectively. Conclusions: EUS-guided nCLE can provide virtual histology of PCLs with a high degree of accuracy and inter- and intraobserver agreement in differentiating mucinous versus non-mucinous PCLs. These preliminary results support larger multicenter studies to evaluate EUS nCLE.