A child chronic cough-specific quality of life measure: Development and validation

Background: Quality of life (QoL) measures are an important patient-relevant outcome measure for clinical studies. Cough is the most common symptom that results in new medical consultations. Although adult and parent-proxy cough-specific QoL instruments have been shown to be a useful cough outcome measure, no suitable cough-specific QoL measure for children with chronic cough exists. We report on the statistical properties of a chronic cough-specific QoL (CC-QoL) questionnaire for children.

Method: 130 children (median age 10 years, IQR 8-12 years; 65 girls) participated. A preliminary 37-item version was developed from conversations with children with chronic cough (>4 weeks). Children also completed generic QoL questionnaires (Pediatric QoL Inventory 4.0 (PedsQL4.0), Spence Children's Anxiety Scale (SCAS)) and cough diary scores.

Results: The clinical impact method of item reduction resulted in 16 items that had excellent internal consistency (Cronbach's α=0.94) among these items and also within each domain. Evidence for construct and criterion validity was established with significant correlations between CC-QoL subscales with cough scores, PedsQL and SCAS scores. CC-QoL scores were sensitive to change following an intervention and significant differences were noted between those children coughing and those who had ceased coughing. Minimum important difference (MID) for overall and domain CC-QoL ranged from 0.37-1.36 (distribution-based approach) to 1.11-1.58 (anchor-based approach).

Conclusions: Chronic cough significantly impacts the QoL of children. The CC-QoL is a reliable, valid and sensitive to change outcome measure that assesses QoL from the child's perspective. Pending data from a confirmatory cohort, a MID for the CC-QoL of 1.1 is recommended when evaluating health status change.