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Assessing Cough Severity and Efficacy of Therapy in Clinical Research

ACCP Evidence-Based Clinical Practice Guidelines

Correspondence to: Richard S. Irwin, MD, FCCP, University of Massachusetts Medical School, Room S6-842, 55 Lake Ave North, Worcester, MA 01655; e-mail address: Irwinr{at}ummhc.org

Objectives: To review the literature on identifying cough and to make evidence-based recommendations for assessing the efficacy of cough-modifying agents in clinical research.

Design/methodology: Ovid MEDLINE literature review (through March 2004) for all studies published in the English language since 1953 using the medical subject heading terms "assessing the impact of cough," "assessing the efficacy of cough treatments," "tussigenic challenges," "cough counting," "character and timing of cough," "visual analog scales," "cough scoring systems," "health related quality of life instruments," "cough-specific health-related quality of life instruments," "citric acid challenge," "capsaicin challenge," "flow-volume loops," "assessing airway inflammation," "lipid laden macrophages in sputum," and "exhaled nitric oxide."

Results/conclusions: To optimally evaluate the efficacy of cough-modifying agents, investigators should use both subjective and objective methods, because they have the potential to measure different things. A patient’s subjective response is likely the only one that measures the impact of the intensity of cough. With respect to subjective methods, it is recommended that a cough-specific health-related quality-of-life instrument be utilized because valid and reliable instruments exist. Even though visual analog scales have not been psychometrically tested, they are recommended because they are commonly used and valid, and they are likely to yield different but complementary results. Because there are cough-specific health-related quality-of-life instruments that have been fully psychometrically tested, and the same cannot be said for visual analog scales, this is a reason to use cough-specific health-related quality-of-life instruments as the primary, subjective outcome measure of choice. With respect to objective methods, tussigenic challenges can be used before and after the intervention to assess the effect of therapy on cough sensitivity. They are most likely to be helpful in disease states in which cough reflex sensitivity is known to be heightened. Because the act of coughing has the potential to traumatize the upper airway (eg, vocal cords), assessing the presence of upper airway edema before and after therapy with flow-volume loops may be useful. Investigators must be cautious and not assume that observing changes suggestive of inflammation and edema of upper airway structures is specific for any particular disease. Cough counting is recommended with a computerized methodology that is reliable and accurate, noninvasive and portable, and easy to use in unattended, ambulatory real-life settings within a subject’s home environment when it can be done over a 24-h period of time.

Key Words: assessing airway inflammation • assessing the efficacy of cough treatments • assessing the impact of cough • capsaicin challenge • citric acid challenge • character and timing of cough • cough counting • cough quality-of-life questionnaire • cough scoring systems • cough-specific health-related quality-of-life instruments • dentifying cough • exhaled nitric oxide • flow-volume loops • health-related quality-of-life instruments • Leicester cough questionnaire • lipid-laden macrophages in sputum • sickness impact profile • tussigenic challenges • visual analog scales

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				R. S. Irwin, M. H. Baumann, D. C. Bolser, L.-P. Boulet, S. S. Braman, C. E. Brightling, K. K. Brown, B. J. Canning, A. B. Chang, P. V. Dicpinigaitis, et al. Diagnosis and Management of Cough Executive Summary: ACCP Evidence-Based Clinical Practice Guidelines Chest, January 1, 2006; 129(1_suppl): 1S - 23S. [Full Text] [PDF]