A Longitudinal Assessment of Acute Cough

Rationale: Cough can be assessed with visual analog scales (VAS), health status measures, and 24-hour cough frequency monitors (CF24). Evidence for their measurement properties in acute cough caused by upper respiratory tract infection (URTI) and longitudinal data is limited. Objectives: To assess cough longitudinally in URTI with subjective and objective outcome measures and determine sample size for future studies. Methods: Thirty-three previously healthy subjects with URTI completed cough VAS, Leicester Cough Questionnaire (LCQ-acute), and CF24 monitoring (Leicester Cough Monitor) on three occasions, 4 days apart. Changes in subjects' condition were assessed with a global rating of change questionnaire. The potential for baseline first-hour cough frequency (CF1), VAS, and LCQ to identify low CF24 was assessed. Measurements and Main Results: Mean +/- SD duration of cough at visit 1 was 4.1 +/- 2.5 days. Geometric mean +/- log SD. baseline CF24 and median (interquartile range) cough bouts were high (14.9 +/- 0.4 coughs/h and 85 [39-195] bouts/24 h). Health status was severely impaired. There was a significant reduction in CF24 and VAS, and improvement in LCQ, from visits 1-3. At visit 3, CF24 remained above normal limits in 52% of subjects. The smallest changes in CF24, LCQ and VAS that subjects perceived important were 54%, 2- and 17-mm change from baseline, respectively. The sample sizes required for parallel group studies to detect these changes are 27, 51, and 25 subjects per group, respectively. CF1 (<20.5 coughs/h) was predictive of low CF24 Conclusions: CF24, VAS, and LCQ are responsive outcome tools for the assessment of acute cough. The smallest change in cough frequency perceived important by subjects is 54%. The sample sizes required for future studies are modest and achievable.