Background: Functional dyspepsia (FD) is a multifactorial disorder with no targeted therapy. Duodenal eosinophilia and low-grade inflammation are potential pathogenic mechanisms. However, the impact of duodenal eosinophils (D-EO) histologic evaluation in real-life clinical practice was not explored. Aim: To evaluate the clinical utility of D-EO and low-grade inflammation in FD in real-life practice. Materials and Methods: A multicenter prospective study was conducted. A total of 636 patients who meet Rome-III criteria were selected before upper endoscopy and 516 patients were included after normal endoscopy were assessed. Clinical parameters, Helicobacter pylori (H. pylori), and duodenal histology were evaluated. Results: FD subtypes were 231 (45%) patients who had epigastric pain syndrome (EPS), 168 (33%) postprandial distress syndrome (PDS), and 117 (22%) EPS/PDS overlap. Two hundred fifty-nine (50.3%) patients were H. pylori +. Histologic duodenal grading of chronic inflammation and intraepithelial lymphocytes showed no difference between FD subtypes. Increased in D-EO densities (>10 per high power field) was significant in PDS compared with EPS and EPS/PDS overlap subtypes. The odds ratio of PDS in subjects with duodenal eosinophilia densities was 2.28 (95% CI, 1.66-3.14; P<0.0001), adjusting for age, gender, H. pylori and nonsteroidal anti-inflammatory drug the odds ratio was 3.6 (95% CI, 2.45-5.28; P<0.0001). receiver operating characteristic curve analysis further demonstrated that low-grade duodenal eosinophilia, in particular H. pylori -, was highly accurate for PDS with the area under the curve 0.731 compared with H. pylori +area under the curve 0.598. Furthermore, low-grade duodenal eosinophilia was significantly correlated with treatment response under 4 to 6 weeks of proton pump inhibitor therapy. Conclusion: Our findings suggest that low-grade duodenal eosinophilia is associated with PDS subtype non-H. pylori FD patients and could be a useful marker of treatment response.Fil: Barreyro, Fernando Javier. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Departamento de Bioquímica Clínica. Laboratorio de Biotecnología Molecular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; ArgentinaFil: Caronia, Maria Virgina. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Departamento de Bioquímica Clínica. Laboratorio de Biotecnología Molecular; ArgentinaFil: Elizondo, Karina. Universidad Nacional de Misiones; ArgentinaFil: Sanchez, Nicolas. Instituto Universidad de la Fundación "Héctor Barceló"; ArgentinaFil: Jordá, Graciela. Universidad Nacional de Misiones; ArgentinaFil: Schneider, Adolfo. Instituto Universidad de la Fundación "Héctor Barceló"; ArgentinaFil: Zapata, Pedro Dario. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Departamento de Bioquímica Clínica. Laboratorio de Biotecnología Molecular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; Argentina