Measuring cough severity: development and pilot testing of a new seven-item cough severity patient-reported outcome measure

Abstract

Objective: Although chronic and subacute cough are clinically problematic and a target of therapeutic interventions, there are no validated cough severity patient-reported outcome (PRO) instruments for comprehensively evaluating cough severity in clinical trials. The Cough Severity Diary (CSD) is a simple, seven-item daily diary developed to meet this need. The objective of this study was to assess preliminary measurement characteristics in a small sample of patients with chronic or subacute cough.

Methods: Thirty-nine patients (24 chronic; 15 subacute) participated in a two-week prospective pilot study. Patients completed the CSD each evening and validation instruments (cough severity visual analog scale [VAS], Leicester Cough Questionnaire [LCQ], Medical Outcomes Study 36-Item Short Form [SF-36], Work Productivity Index [WPAI], MOS Sleep Scale [MOS-SS]) at baseline, days 8 and 15, and a global rating of change at days 8 and 15.

Results: Confirmatory factor analyses supported three severity subscales: frequency (three items), intensity (two items), and disruption (two items) (χ² = 10.57 (11)). For the CSD total score, internal consistency (α) on day 1 was 0.89, and on day 8 was 0.96; reproducibility (intraclass correlation coefficients [ICC]) was 0.68 on day 1 to day 8 and 0.94 on day 8 to day 15. CSD total scores correlated with the VAS (r = 0.84, p < 0.0001), LCQ total (r =-0.62, p < 0.0001) and subscale scores (r =-0.43, p < 0.01 to -0.60, p < 0.0001), and WPAI subscale scores (r = 0.27 (ns) to 0.51, p < 0.01). No significant relationships with SF-36 or MOS-SS were found. Subacute patients showed significant improvement over time (F = 3.20, p < 0.05).

Conclusions: Results suggest that the CSD is ready for further testing in larger naturalistic studies or as an exploratory endpoint in clinical trials of patients with subacute or chronic cough.

Keywords

cough diary patient-reported outcome psychometric questionnaire respiratory validation

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