Minimally important change in a Parent-Proxy Quality-of-Life questionnaire for pediatric chronic cough.
BACKGROUND
The Parent Cough-Specific Quality-of-Life questionnaire (PC-QOL) has relevance and clinical utility as a cough-specific QOL measure for pediatric use. Its validity has been demonstrated. This study sought to determine the minimally important difference (MID) for the PC-QOL completed by parents of young children with chronic cough.


METHODS
Thirty-four children (22 boys, 12 girls; median age, 26.5 months; interquartile range, 17.3-38.8 months) and their mothers participated. Mothers completed a cough-related measure (verbal category descriptive score) and the PC-QOL on two occasions separated by 2 to 3 weeks. Two approaches were used to calculate MID.


RESULTS
Distribution-based approaches to estimating MID resulted in ranges of 0.50 to 0.78 (effect size method), 0.30 to 0.48 (SE of measurement method), and 0.60 to 0.69 (one-half SD method) for PC-QOL overall and domain scales. Based on verbal category descriptive score change, an anchor-based approach resulted in an MID estimate of 0.9 for overall PC-QOL change and ranged from 0.71 to 0.95 for individual domain PC-QOL change.


CONCLUSIONS
An MID for the PC-QOL of 0.9 is recommended in interpreting health status change in children with chronic cough and will aid clinicians and researchers in interpreting health-related QOL changes following treatments and clinical trials.
School of Social Work and Applied Human Sciences, University of Queensland, Brisbane, QLD; School of Psychology, University of Queensland, Brisbane, QLD. Electronic address: newc@psy.uq.edu.au.
Peter A
PA
Newcombe
School of Psychology, University of Queensland, Brisbane, QLD.
Jeanie K
JK
Sheffield
Queensland Children's Respiratory Centre and Queensland Children's Medical Research Institute, Royal Children's Hospital, Brisbane, QLD; Child Health Division, Menzies School of Health Research, Darwin, NT, Australia.
Anne B
AB
Chang
D002675:Child, Preschool; D002908:Chronic Disease; D003371:Cough / Q000523:psychology*; D005260:Female; D006304:Health Status; D006801:Humans; D007223:Infant; D008297:Male; D010290:Parents / Q000523:psychology*; D019727:Proxy / Q000523:psychology*; D011788:Quality of Life / Q000523:psychology*; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires