Determination of a treatment response threshold for the Eosinophilic Esophagitis Endoscopic Reference Score.

BACKGROUND: Endoscopic features of eosinophilic esophagitis (EoE) are measured using the validated EoE Endoscopic Reference Score (EREFS); however, a threshold for treatment response has not been defined. We aimed to determine a cut-point for endoscopic response as measured by EREFS. METHODS: We performed a secondary analysis of a randomized clinical trial comparing budesonide slurry with swallowed fluticasone multidose inhaler for initial treatment of EoE. In the parent trial, EREFS was determined before and after treatment (score range 0-9), as were histologic findings and dysphagia symptoms. We performed tabular, flexible trend, and dependent mixture analyses of measures of treatment response to select the best clinical EREFS threshold. RESULTS: In the 111 included patients (mean age 39 years; 67 % male; 96 % white), an EREFS threshold of ≤ 2 was 80 % sensitive (95 % confidence interval [CI] 69 % to 88 %) and 83 % specific (95 %CI 67 % to 94 %) for histologic response (peak of < 15 eosinophils per high-power field). Flexible trend analysis and dependent mixture modeling similarly suggested that a threshold of ≤ 2 best captured the correlation of EREFS with histologic and symptomatic measures. Dependent mixture modeling found near-total membership in the response class at EREFS of 0 or 1 and > 75 % at EREFS of 2 or 3. CONCLUSIONS: An EREFS of ≤ 2 was the best clinical threshold for endoscopic response to topical steroid treatment, and was consistent with clinical and histologic response. Therefore, future studies can report a binary outcome of endoscopic response when EREFS is 2 or less.