Frazzoni M, Penagini R, Frazzoni L, et al. - Researchers sought to ascertain the role of reflux and mechanisms of response to proton pump inhibitor (PPI) therapy in eosinophilic esophagitis (EoE) via performing the comprehensive assessment by impedance-pH monitoring. In this prospective multicenter study, 60 patients with EoE were compared with 60 healthy controls and 60 patients with gastroesophageal reflux disease. Relative to healthy controls, patients with EoE had higher number of total refluxes and had lower postreflux swallow-induced peristaltic wave (PSPW) index. Off PPI, they observed a lower mean nocturnal baseline impedance (MNBI) gradient between the mid and distal esophagus separating 20 patients with PPI-refractory EoE from 40 patients with PPI-responsive EoE; this was a predictor of PPI failure. On PPI, the sole reflux parameter distinguishing PPI-refractory from PPI-responsive EoE was a lower PSPW index; they observed improvement in all reflux parameters in PPI-responsive patients, whereas no modification in the PSPW index was noted in PPI-refractory cases; this index was independently associated with PPI-responsiveness. In PPI-responsive vs PPI-refractory EoE, much more improvement in MNBI in the distal and mid esophagus was observed. These findings suggest a role of reflux in the pathogenesis of EoE; this role seemed more relevant in PPI-responsive cases. PPI refractoriness could be assessed using low impedance gradient between the mid and distal esophagus. PPIs chiefly improve chemical clearance, ie, have an antireflux action supporting long-term prescription in PPI-responsive EoE.