Validation of the Leicester Cough Monitor (LCM): preliminary findings using an automated cough detection system in patients with chronic cough

¹ Dept of Respiratory Medicine, King's College Hospital, London, United Kingdom
² Dept of Medical Physics, Leicester Royal Infirmary, Leicester, United Kingdom
³ Institute for Lung Health, Department of Respiratory Medicine, Glenfield Hospital, Leicester, United Kingdom.

^* To whom correspondence should be addressed. E-mail: ian.pavord{at}uhl-tr.nhs.uk.

	Abstract

Chronic cough is a common condition that presents to both primary and secondary care. Assessment and management are hampered by the absence of well-validated outcome measures. We present the validation of the Leicester Cough Monitor (LCM), an automated sound based ambulatory cough monitor.

We measured cough frequency with the LCM and compared it to coughs and other sounds counted manually over 2 hours of a 6-hour recording by two observers in 9 patients with chronic cough to determine the sensitivity and specificity. Automated cough frequency was also compared to manual counts from one observer in 15 patients with chronic cough and 8 healthy subjects. All subjects had 6-hour recordings. A subgroup of 6 normals and 5 patients with a stable chronic cough had repeat automated measurements at least 3 months apart. A further 50 patients with chronic cough had 24-hour automated cough monitoring.

The LCM had a sensitivity and specificity of 91% and 99% for detecting cough and a false positive rate of 2.5 events·hour^-1. Mean (SEM) automated cough counts·hour^-1 were 48(9) in patients with chronic cough and 2(1) in normals (mean difference 46; 95% confidence interval 20 to 71; p<0.001). The automated cough counts were repeatable (within subject standard deviation 11 coughs·hour^-1; intraclass correlation coefficient 0.9; p=0.001). The cough frequency in patients undergoing 24-hour automated monitoring was 19 coughs·hour^-1; day-time (8am-10 pm) cough frequency was significantly greater than overnight cough frequency (25 vs 10 coughs·hr^-1; mean difference 15, 95% confidence interval of difference 8 to 22; p<0.001).

The LCM is a valid and reliable tool that can be used to assess 24-hour cough frequency in patients with cough. It should be a useful tool to assess patients with cough in clinical trials and longitudinal studies.

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