Background: Cough reflex sensitivity, subjective estimates of cough frequency and cough related quality of life have been used to assess cough and monitor treatment responses. The relationships between these measures and objective cough monitoring remains unclear and the usefulness of subjective assessments, questionable.
Subjects: 62 patients with chronic cough (39 female) were studied. Mean age of subjects was 54.9 years (±12.2), with a median duration of cough of 5.5 years (range 1-30).
Methods: Cough reflex sensitivity testing (C5; citric acid) was performed in all subjects prior to fully ambulatory day and night-time cough recordings. Patients scored the frequency and severity of their cough (visual analogue scales and 0-5 score) for each recording period and completed a cough related quality of life questionnaire, Leicester Cough Questionnaire (LCQ). Ambulatory cough recordings were manually counted and reported in terms of cough seconds per hour (cs/hr). Cough rates were Log10 transformed for analysis.
Results: The median time spent coughing was 11.36cs/hr (range 1.06-46) with median day rates of 15.59cs/hr (range 2-74.8) and median night rates of 2.94cs/hr (range 0-26.67). An inverse relationship was seen between day cough rates and Log10 C5 (r=-0.452 p=<0.001). Subjective cough scores and visual analogue scales were only moderately associated with objective time spent coughing, with night-time scores more strongly associated than day. The strongest correlation with objective cough frequency was cough related quality of life (LCQ), (r=-0.622, p=<0.001), mediated via the psychological domain.
Conclusions: Subjective measures of cough and cough reflex sensitivity are only moderately related to objective time spent coughing, so cannot be used as surrogate markers for objective cough frequency measurements. Cough related quality of life (LCQ) is most strongly related to objectively counted cough, and may be a useful adjunct to objective measures in the assessment of cough.
- ambulatory monitoring
- chronic cough
- citric acid
- cough challenge