Eosinophilic esophagitis (EoE) is an increasingly recognized rare disease of children and adults characterized by symptoms including nausea, vomiting, abdominal pain, dysphagia and food impaction that occur in conjunction with esophageal eosinophilia. To date, the only method to make EoE diagnoses and follow treatment responses in EoE is invasive endoscopy with biopsy. While endoscopy is generally safe, an accurate, less invasive, inexpensive, comprehensive and durable test is urgently needed to determine therapeutic efficacy. To address this need, we will use a novel application of an existing technology, the Enterotest (a string-based test used to detect intestinal Giardiasis), to measure esophageal inflammation (herein termed the Esophageal String Test - EST). Our supportive Preliminary Data provide proof-of-principle for the ability of ESTs to capture esophageal inflammatory mediators in luminal samples from patients affected with EoE. Our prospective study demonstrates that: (1) levels of eosinophil-derived granule proteins (MBP1, EDN, ECP, EPX, CLC/Gal-10) in esophageal mucosal biopsies correlate with levels quantitated in EST-captured samples, i.e., levels in luminal secretions captured by the EST correlate with mucosal inflammation, and (2) these luminal biomarkers of eosinophilic inflammation significantly correlate with EoE disease activity. These findings provide strong support for using ESTs as novel minimally invasive instruments to monitor therapeutic efficacy in EoE. The global objective of this project is therefore to bring the "Esophageal String Test" (EST) to commercialization, so that it can be used to monitor therapeutic efficacy in children and adults with EoE. We hypothesize that ESTs will capture an EoE Biomarker Panel (EBP) reflective of disease activity. The Specific Aims are to: (1) Identify an EoE Biomarker Panel (EBP) that will improve the sensitivity and specificity of the EST for monitoring disease activity and (2) Validate the ability of the EST EBP to monitor therapeutic efficacy in 1-hour sampling time.