A Longitudinal Assessment of Acute Cough

Abstract 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.