TABLE 2

Cough measurements in idiopathic pulmonary fibrosis (IPF) patients

Cough measurement toolDescriptionValidation studies and MCIDAdvantagesDisadvantages
Subjective    
 Visual analogue scale [56]100 mm scale with extremes no cough to worst possible cough severityNot validated in IPFEasy to use
Repeatable
Responsive		Not validated in IPF or chronic cough
 Cough quality-of-life questionnaire [57]28-item cough-specific quality-of-life questionnaire with six domainsValidated in IPF (n=23)
MCID in IPF: change of five points on a 28–112 scale [57]		Comprehensive questionnaire
Reliable
Valid instrument for assessing impact of cough		Need more studies in IPF: MCID evaluated with a retrospective anchor scale
 Leicester cough questionnaire [15]19-item self-administered chronic cough quality-of-life questionnaire with three domainsEvaluated in IPF: high correlation found with cough visual analogue scale, cough symptom score and objective cough frequency in IPF [10, 22]
MCID in chronic cough: 1.3		High reliability
Valid instrument for assessing impact of cough
Ability to detect a response to change		Need more studies in IPF: MCID evaluated in chronic cough
Objective
 Cough challenge test [58]Measurement of cough reflex sensitivity by inhalation of nebulised tussive agents (most common citric acid or capsaicin)Not validated in IPF
No MCID
Standardised methodology published by ERS [14]		Useful for testing effect of new cough therapies on cough reflex sensitivity and for obtaining mechanistic insightsDoesn't measure efficacy of therapy or predict response in patients
Limited availability
 Cough monitor [59]Microphone and recording device measuring cough in a pre-specified time slotValidated cough monitors for chronic cough
High correlation found with subjective cough measurements [10]		Measures cough frequency accuratelyCurrently limited to research and trails
Benefit in routine clinics is not clear

  • MCID: minimal clinically important difference; ERS: European Respiratory Society.