INTRODUCTION:In patients with familial adenomatous polyposis, the Spigelman classification is recommended for staging and risk stratification of duodenal adenomatosis. Although the classification has been used for decades, it has never been formally validated.METHODS:We included consecutive FAP patients undergoing upper gastrointestinal endoscopic surveillance and evaluated the inter-and intrarater reliability of the Spigelman classification.RESULTS:The interrater reliability of the endoscopic parameters and the Spigelman classification was good and excellent, respectively. The intrarater reliability of the endoscopic parameters and the Spigelman classification was moderate and good, respectively.DISCUSSION:The results support continued use of the Spigelman classification as the primary end point for future studies and as key endoscopic performance measure.