Neuropeptide levels in nasal secretions from patients with and without chronic cough.

BACKGROUND

The pathophysiology of upper airway cough syndrome is not well understood.

OBJECTIVE

To investigate the levels of neuropeptides found in nasal mucus of subjects with and without the complaint of chronic cough.

METHODS

Preformed nasal mucus from 26 subjects complaining of postnasal drip with chronic cough and 17 without self-reported chronic cough was collected at the time of presentation. The nasal secretions were assayed for 3 neuropeptides-substance P (SP), calcitonin gene-related peptide (CGRP), and Neurokinin A (NKA)-that have been previously linked to chronic cough.

RESULTS

Coughing subjects with postnasal drip have significantly higher levels of CGRP and SP than noncoughing subjects with postnasal drip (69.0 ng vs 4.6 ng, P < .001 and 4.5 ng vs 3.4 ng, P = .004). The differences in NKA levels in nasal secretions between coughing and noncoughing subjects did not reach statistical significance (16.3 ng vs 3.4 ng, P = .067).

CONCLUSIONS

Both CGRP and SP levels are elevated in preformed nasal secretions of coughing subjects when compared with noncoughing subjects. Additional studies are needed to clarify whether CGRP and SP levels in preformed nasal secretions may assist in diagnosis or predicting treatment response in patients presenting with chronic cough.