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Evaluation of a cough-specific quality-of-life questionnaire
Cynthia T French1, Richard S Irwin, Kenneth E Fletcher
1Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01655, USA.
Study Objective:
To psychometrically evaluate a cough-specific quality-of-life questionnaire (CQLQ) in adults.
Design:
Prospective evaluation of CQLQ using three different cohorts of adult subjects with cough.
Setting:
Academic tertiary-care ambulatory medical facilities.
Participants:
One hundred fifty-four subjects complaining of chronic cough, 30 of acute cough, and 31 smokers with cough.
Interventions:
Self-administration of the CQLQ in acute coughers, smokers, and chronic coughers before and after therapy.
Measurements:
Psychometric analyses including factor analysis (FA), and assessments of reliability and validity.
Results:
Acute and chronic cough data were subjected to FA, and the Cronbach alpha and interitem correlations were computed. FA of chronic and acute cough data (n = 184) revealed six subscales. The Cronbach alpha for the total CQLQ was 0.92, and it was 0.62 to 0.86 (mean, 0.76) for the six subscales. Interitem correlations for the total CQLQ ranged from -0.06 to 0.72, with a mean of 0.28. Test-retest reliability in 52 chronic coughers demonstrated nonsignificant changes with readministration of the questionnaire, and the intraclass correlation for total CQLQ was 0.89, and for the subscales the range was 0.75 to 0.93. Analysis of variance followed by tests of contrasts among all possible pairings of chronic coughers, acute coughers, and smokers showed significant differences (p < or = 0.001) among the groups. Posttreatment cure scores were significantly lower (p < or = 0.001) than pretreatment scores in 24 chronic coughers.
Conclusions:
The 28-item CQLQ has dimensionality that is consistent with a cough-specific quality-of-life instrument. It is a valid and reliable method by which to assess the impact of cough on the quality of life of chronic and acute coughers, and the efficacy of cough therapies in chronic coughers.