Interobserver agreement for the assessment of erosive reflux esophagitis: a <i>post hoc</i> analysis of clinical trial data

Interobserver agreement for the Los Angeles (LA) classification of erosive reflux esophagitis was good in validation studies, but limited agreement data exists from clinical trials (CTs). We conducted a post hoc evaluation of interobserver agreement between CT endoscopists and independent expert adjudicators in a multi-center, randomized controlled trial of a new acid suppression therapy. Trial endoscopists captured endoscopic images/videos and documented esophagitis severity using the LA classification. Adjudicators reviewed images/videos on a web-based platform. If the first two adjudicators disagreed and the third adjudicator did not produce a majority verdict, all three conferred to reach consensus. Cohen's kappa (κ) evaluated interobserver agreement. Cohen's weighted kappa (κw) evaluated agreement corrected for disagreement extent. Of 388 images/videos with adequate quality, trial endoscopists and adjudicators agreed on esophagitis severity in 168 (43.3%) cases, and assigned more severe grades than adjudicators for 185 (47.7%) cases. Agreement was fair between trial endoscopists and adjudicators (κ: 0.27; κw: 0.40), moderate between individual adjudicators (κ: 0.43 to 0.47), and good between adjudicators and final diagnosis (κ: 0.75 to 0.78). After adjusting for disagreement extent, agreement was good between individual adjudicators (κw: 0.63 to 0.66), and very good between adjudicators and final diagnosis (κw: 0.84 to 0.87). Interobserver agreement on esophagitis severity between CT endoscopists and adjudicators was fair. Initial agreement between adjudicators was moderate, but agreement between adjudicators and consensus diagnosis was very good. Accurate esophagitis grading for CTs requires further training on LA classification and a robust central reading protocol.