Endoscopic assessment of the "Z-line" (squamocolumnar junction) appearance: reproducibility of the ZAP classification among endoscopists.

Background: The histologic presence of intestinal metaplasia in the esophagus is a prerequisite for the diagnosis of Barrett's esophagus. Thus, use of the term Barrett's esophagus to describe certain endoscopic features in the distal esophagus is inappropriate. There is no accepted classification system for the endoscopic description of the squamocolumnar mucosal junction, the so-called "Z-line." Furthermore, no clear definition of the normal Z-line exists. A classification of the Z-line appearance has been proposed: the ZAP classification. The aim of this study was to assess the reproducibility of this classification.

Methods: Ten physicians with varying endoscopy experience were presented with 15 endoscopic photographs of the Z-line and were asked to classify them according to the ZAP classification. A second assessment was conducted between 7 and 15 weeks after the first.

Results: The median kappa values were in the range of 0.72 to 0.90 with regard to intraobserver as well as interobserver reproducibility, irrespective of experience with upper endoscopy.

Conclusions: The intraobserver and interobserver reproducibility of the ZAP classification is substantial and thus it is feasible to use this classification to characterize the appearance of the Z-line at endoscopy.