Validation of a visual analog scale for assessing cough severity in patients with chronic cough

Abstract

Introduction: Patients with chronic cough experience considerable burden. The cough severity visual analog scale (VAS) records patients’ assessment of cough severity on a 100-mm linear scale ranging from “no cough” (0 mm) to “worst cough” (100 mm). Although cough severity scales are widely used in clinical practice and research, their use in patients with refractory or unexplained chronic cough has not been formally validated. Methods: This analysis includes data from a phase 2b randomized controlled trial of the P2X3-receptor antagonist gefapixant for treatment of refractory or unexplained chronic cough (NCT02612610). Cough severity VAS scores were assessed at baseline and Weeks 4, 8, and 12. The cough severity VAS was validated using several outcomes, including the Cough Severity Diary (CSD), Leicester Cough Questionnaire (LCQ), patient global impression of change (PGIC) scale, and objective cough frequency. Validation metrics included test–retest reliability, convergent and known-groups validity, responsiveness, and score interpretation (i.e., clinically meaningful change threshold). Results: The analysis included 253 patients (median age, 61.0 years; females, 76%). Test–retest reliability of the cough severity VAS was moderate (intraclass correlation coefficient, 0.51). The cough severity VAS had acceptable convergent validity with other related measures (Pearson r of 0.53 and -0.41 for CSD and LCQ total scores, respectively; p < 0.0001 for each). Known-groups validity was supported by significant differences in mean cough severity VAS scores across severity groups defined using CSD, LCQ, and cough frequency tertiles. A large effect size was observed in patients with the greatest improvements in PGIC (Cohen d = -1.8). A ⩾ 30-mm reduction in the cough severity VAS was estimated as a clinically meaningful change threshold for clinical trials in chronic cough. Conclusions: The cough severity VAS is a valid and responsive measure. A cough severity VAS reduction of ⩾ 30 mm can discriminate clinically meaningful changes in chronic cough severity in clinical studies.

Sinonasal Symptoms in COPD: Burden and Associations with Clinical Markers of Disease

“… 24 Cough severity was measured on a VAS from 0 (cough not troublesome) to 100 mm (cough worst thinkable troublesome). 25 …”

Effectiveness and Safety of Codeine and Levodropropizine in Patients With Chronic Cough

“…To aid clinical interpretability of the patient-reported outcomes, response rates to antitussives were calculated as the proportions of patients exceeding the minimum clinically important difference (MCID) threshold of VAS and LCQ and achieving a 50% improvement from the baseline of total CSS (CSS 50). As proposed by Raj et al 19 and Martin Nguyen et al, 17 the MCID expressed as the total scores of the cough VAS and LCQ in chronic cough were 30 and 1.3, respectively. The time required for the perceived effect on symptom alleviation was also compared between the two groups.…”

“…The VAS is widely used for the subjective assessment of cough because it is a simple and brief measure of patient-reported outcomes. 17 18 Participants were asked to indicate cough severity by marking between 0 (no cough) and 100 (the worst cough severity) on a 100 mm scale. Secondary outcomes included between-group differences in effectiveness regarding CSS and LCQ changes.…”

Improvements in Objective and Subjective Measures of Chronic Cough with Gefapixant: A Pooled Phase 3 Efficacy Analysis of Predefined Subgroups

“…As a single-item assessment, the cough severity VAS is a relevant cough measure for clinical practice and was recently validated as a reliable and responsive measure in patients with chronic cough [ 12 ]. In the cough severity VAS subgroups, placebo responses were comparable (55% and 54% for < 60 and ≥ 60 mm, respectively), and those with more severe cough demonstrated a greater response to gefapixant compared with those with less severe cough; however, the numbers of participants in the subgroups were not well balanced and the confidence intervals were wide.…”