Quantifying chronic cough: objective versus subjective measurements

The assessment of chronic cough has been improved by the development of objective ambulatory cough monitoring systems and subjective quality of life questionnaires. Experimental induction of cough is a useful tool in the assessment of the cough reflex. We wanted to assess the reproducibility of and association between these measurements.

This was a prospective observational study in patients with chronic cough of greater than 6 months' duration. All patients had an initial 24-h cough recording. They also completed a Leicester Cough Questionnaire, a Symptom Assessment Score, a Visual Analogue Score for cough and had a capsaicin cough challenge performed. They were reviewed at 8 weeks when all assessments were repeated.

Twenty-five patients (15 women) with a mean age of 54 years were included in the study. The median cough count at the second visit (302) was significantly lower compared to the first visit (381, P < 0.01). However, the cough counts at both the visits correlated well (r = 0.9, P < 0.01). All the other forms of assessment were found to be highly reproducible at 8 weeks (r = 0.6-0.9, P < 0.01). Cough counts correlated well with the other forms of assessment (r = 0.4-0.6, P < 0.01). There was good correlation between each of the subjective forms of assessment (r = 0.6, P < 0.01).

The various forms of assessment of cough are reproducible. Cough counting correlates well with subjective assessment of cough and cough reflex sensitivity. It appears to lie between these latter two assessments of cough and may represent the best global objective synthesis of cough.