Grant: Project Grant

Chronic cough affects 16% of Canadians over the age of 45. Some patients respond well to treatments addressing known causes of cough. However, up to 60% of patients have, despite optimal therapy, cough that persists (refractory chronic cough) or cough with no identifiable cause (unexplained chronic cough). There remain no licensed therapies for these patients and current management includes neuromodulators (i.e., morphine) that have modest effectiveness and pose substantial harms. New therapies are urgently needed. Studies evaluating the efficacy of novel antitussives currently use cough frequency monitoring as the primary endpoint. Although cough frequency monitors objectively assess cough, they are limited by their sampling (24 hours), expense, burden, and lack of use in clinical practice. Patient reported outcome (PRO) measures that assess other aspects of cough (i.e., patients' perception of cough severity) are needed to provide full assessment of the efficacy of new therapies. Existing PRO measures for cough primarily assess the impact of cough on quality of life. A major limitation of these measures includes that they do not assess whether treatment improves severity of the cough symptom itself. Regulatory agencies (i.e., the FDA) have thus deemed existing PRO measures not adequate for drug approval. Using FDA guidance, we have developed the McMaster Cough Severity Questionnaire (MCSQ) for patients with chronic cough. The 8-item MCSQ has two domains (intensity and frequency), a one-week recall period, and is scored on 7-point Likert scales. Initial evidence supports the cross-sectional validity of the MCSQ; however, its properties in measuring change over time have not yet been established. We propose two prospective studies in patients with chronic cough to assess its longitudinal validity, reliability, and responsiveness. The MCSQ will provide an important measure for use in clinical trials and clinical practice to assess the effectiveness of therapies.