Introduction The Leicester Cough Monitor (LCM) is a validated 24-h automated cough frequency monitor. Shorter recordings are more convenient for patients and take less time to analyse but their validity for assessing cough is not known. We assessed the relationship between short duration and 24-h recordings.
Methods 100 patients (57 females) with chronic cough underwent 24-h ambulatory cough frequency monitoring with the LCM. Patients completed diaries to identify awake and sleep periods. Cough frequency was determined by automated analysis and presented as 24-h cough frequency (CF24), awake cough frequency, sleep cough frequency, and short duration (1–6 h). Subjective cough severity was assessed by cough visual analogue scale and quality of life questionnaire (Leicester Cough Questionnaire, LCQ). The optimal short cough recording duration was determined by assessing its relationship with awake cough frequency and subjective cough severity. The responsiveness of short duration recordings was tested in 20 patients undergoing trials of therapy.
Results The median (IQR) 24-h cough frequency was 11.5 (5.8 to 26.6) coughs/h, awake cough frequency 13.2 (7.6 to 37.5) coughs/h and sleep cough frequency 4.2 (1.0 to 9.2) coughs/h. 4-h cough counts correlated strongly with both awake and 24-h cough counts; r2=0.88 and r2=0.87 respectively (Abstract S117 Figure 1). There was a moderate relationship between 4-h cough frequency (CF4) and LCQ and cough VAS (r=−0.48, p<0.001 and 0.49, p<0.001) which was comparable to that between awake cough frequency and LCQ and cough VAS. The effect size of change in CF4 after therapeutic trials was 0.55.
Conclusions Shorter duration cough frequency recordings with the LCM accurately reflect daytime and 24-h cough frequency in patients with chronic cough. They can be used to assess daytime cough frequency and the response to trials of therapy.
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