Altered Viscosity of Nasal Secretions in Postnasal Drip

Postnasal drip (PND) is a common symptom associated with upper respiratory tract disorders. It occurs without other symptoms or combined with chronic rhinosinusitis. However, the pathophysiology of PND is debated to this day, and an objective definition of PND has not been established. Therefore, we aimed to elucidate whether the viscosity and volume of nasal secretions as well as the mucociliary clearance and sensitivity of the nasopharynx, or atopy could play a role in the pathophysiology of PND.

A prospective case-control study of 30 patients (15 patients with PND and 15 healthy subjects) was conducted. The viscosity and volume of nasal secretions, the nasopharyngeal sensitivity, the mucociliary clearance, and allergic sensitization using a skin prick test were assessed in all subjects.

Viscosity of nasal secretions in patients with PND was significantly increased compared with healthy subjects. Two follow-up measurements in symptom-free intervals showed reversibility of increased viscosity. Analysis of nasopharyngeal sensitivity showed significant reductions in patients with PND. Furthermore, mucociliary clearance seems to be prolonged in patients with PND. The volume of nasal secretions and the atopy screening showed no significant differences in patients with PND compared with healthy individuals.

Increased viscosity seems to play a relevant role in the pathophysiology of PND. Additionally, delayed mucociliary clearance and hyposensitivity of the nasopharynx may be further components. Earlier concepts of PND, regarding an increased volume of secretions and atopy, do not seem to hold true because our analyses showed no significant difference between cases and control subjects.