Measuring cough: what really matters?

The clinical and research discipline of cough has grown substantially over the last two decades as methods to measure cough have developed and evolved. Cough can be thought of both as a symptom and an objectively observable pathophysiological phenomenon, two aspects whose interrelationship is complicated. The following review explores the varied methods to measuring cough, both subjective, patient-reported measures and objective approaches. Specifically, symptom scores, questionnaires of cough-related quality of life, and associated mental health impacts of chronic cough are addressed, as are developments in measuring cough frequency, cough intensity, cough reflex sensitivity, and cough suppressibility. Measuring patient reported cough-severity with a simple visual analogue scale increasingly appears to be justified, but has limitations. The Leicester Cough Questionnaire has been widely used for twenty years, within varied settings and diseases, in research and routine clinical practice, and captures cough-related quality of life. Objective cough frequency has become the primary outcome measure for clinical trials of antitussives, and technology is now enabling the wider application of cough counting. Inhaled tussive challenge testing still has a role, including in the assessment of cough hypersensitivity, and in the identification of failure to supress cough. Ultimately, many measures have a contributory and complementary role, with differing merits in quantifying the multiple facets of cough, the complexity of which is being increasingly recognised.