Results indicate that pepsin/pepsinogen is present in the middle ears of children with otitis media, although not at the high rate previously reported. Gastric reflux may be one causative factor in the pathogenesis of otitis media.

Pepsin is detectable in the middle ear cleft of 20% of pediatric patients with OM undergoing tympanostomy tube placement, compared with 1.4% of controls; recovery of pepsin in the middle ear space of pediatric patients with OM is an independent risk factor for OM. Patients under 1 year of age have a higher incidence of purulent effusions and pepsin-positive effusions. Clinical history of GERD, allergy, and asthma do not seem to correlate with evidence of EORD reaching the middle ear cleft. The presence of pepsin in the middle ear space at the time of tube placement does not seem to predispose to posttympanostomy tube otorrhea.

The concentration of pepsin was increased in the tracheal aspirate of preterm infants who developed bronchopulmonary dysplasia or died before 36 weeks' postmenstrual age. Recovery of pepsin in tracheal aspirate samples is secondary to gastric aspiration, not by hematogenous spread or local synthesis in the lungs. Chronic aspiration of gastric contents may contribute in the pathogenesis of bronchopulmonary dysplasia.

Measurement of gastric pepsin in tracheobronchial fluid is a sensitive tool to detect aspirations in mechanically ventilated children and to assess the efficacy of preventive measures in PICU settings.