BACKGROUND: Acute respiratory illnesses cause substantial morbidity worldwide. Cough is a common symptom in these childhood respiratory illnesses but there is currently no large cohort data on whether various cough characteristics can differentiate between these aetiologies.
RESEARCH QUESTION: Can various clinically-based cough characteristics (frequency [day-time/ night-time], the sound itself, or type [wet/dry]) be used to differentiate common aetiologies (asthma, bronchiolitis, pneumonia, other acute respiratory infections) of acute cough in children?
STUDY DESIGN AND METHODS: Between 2017-2019, children aged 2-weeks to ≤16-years hospitalised with asthma, bronchiolitis, pneumonia, other acute respiratory infections, or controls were enrolled. Spontaneous coughs were digitally recorded over 24-hours except for the controls, who provided three voluntary coughs. Coughs were extracted and frequency defined (coughs/hour). Cough sounds and type were assessed independently by two observers blinded to the clinical data. Cough scored by a respiratory specialist was compared to discharge diagnosis using agreement (Cohen's kappa coefficient [қ]), sensitivity, and specificity. Caregiver reported cough scores were related with objective cough frequency using Spearman's coefficient (rs).
RESULTS: A cohort of 148 children (n=118 with respiratory illnesses, n=30 controls), median age=2.0 years (interquartile range 0.7, 3.9), 58% males, and 50% First Nations children were enrolled. In those with respiratory illnesses, caregiver reported cough scores and wet cough (range 42-63%) was similar. Overall agreement in diagnosis between the respiratory specialist and discharge diagnosis was slight (қ=0.13, 95%CI 0.03, 0.22). Among diagnoses, specificity (8-74%) and sensitivity (53-100%) varied. Inter-rater agreement in cough type (wet/dry) between blinded observers was almost perfect (қ=0.89, 95%CI 0.81, 0.97). Objective cough frequency was significantly correlated with reported cough scores using visual analogue scale (rs=0.43, bias-corrected 95%CI 0.25, 0.56) and verbal categorical description day-time score (rs=0.39, bias-corrected 95%CI 0.22, 0.54).
INTERPRETATION: Cough characteristics alone are not distinct enough to accurately differentiate between common acute respiratory illnesses in children.