Chest
Volume 143, Issue 6, June 2013, Pages 1745-1749
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Original Research
Signs and Symptoms of Chest Diseases
Validation of the Cough Quality-of-Life Questionnaire in Patients With Idiopathic Pulmonary Fibrosis

https://doi.org/10.1378/chest.12-2870Get rights and content

Background

Cough is a pervasive and disabling symptom of idiopathic pulmonary fibrosis (IPF) and is an independent predictor of disease progression. The Cough Quality-of-Life Questionnaire (CQLQ) is a validated measure of cough-specific quality of life that could be used as an outcome measure in therapeutic trials for IPF. This study aimed to assess the reliability and validity of the CQLQ in individuals with IPF.

Methods

The CQLQ was administered as an outcome within a previously published 27-week, placebo-controlled, crossover trial of thalidomide for cough in IPF. Participants were adults with IPF and chronic cough. A cough visual analog scale (VAS) and the St. George's Respiratory Questionnaire (SGRQ) were administered to establish concurrent validity of the CQLQ.

Results

Internal consistency was high (Cronbach α > .70) for the CQLQ total and four of six subscale scores. The CQLQ total score demonstrated concurrent validity through significant correlations with scores on the cough VAS and SGRQ total and subscale scores (r range, 0.63-0.81; P < .05). The intraclass correlation coefficient for the CQLQ completed at baseline and after a therapeutic washout period at week 15 was 0.87, indicating very good test-retest reliability.

Conclusions

This study supports the use of the CQLQ as a valid and reliable instrument in IPF and should be used to assess cough-specific quality of life in therapeutic trials.

Section snippets

Materials and Methods

This study was performed within the context of a randomized clinical trial of thalidomide to treat cough in IPF.10 It was approved by the Johns Hopkins Medicine Institutional Review Board (Approval # NA 00007590). The trial was a double-blinded, two-treatment, two-period crossover study with two 12-week treatment periods separated by a 2-week drug-free washout period. Participants were recruited between February 2008 and March 2011. All participants provided written informed consent.

Results

Ninety-eight individuals inquired about the study between February 2008 and March 2011. Of the 25 participants who signed informed consent, 24 were eligible for the trial and were randomized. Of the 24 randomized participants, 23 were treated (one left the study because of lack of interest), and 20 completed both treatment periods (three dropped out because of worsening health). The demographic characteristics of participants are shown in Table 1, and further details about the study population

Discussion

Cough is a frequent, disabling symptom in patients with IPF,5 and it is important to be able to precisely quantify the impact of cough-specific quality of life in clinical trials and in the clinical care of patients with IPF.13 The current study demonstrates the validity and reliability of the CQLQ for individuals with IPF.

Construct analysis of the CQLQ showed good internal consistency for the total score and most of the subscales (Table 3). However, the extreme physical complaints and personal

Acknowledgments

Author contributions: Dr Lechtzin had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Dr Lechtzin: contributed to the study conception and design; data acquisition, analysis, and interpretation; drafting of the manuscript; critical revision of the manuscript for important intellectual content; and approval of the final version.

Dr Hilliard: contributed to the study conception and design; data acquisition,

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Funding/Support: The Celgene Corporation provided support for the initial clinical trial from which these data were obtained.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.

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