• Aleksandra Jokovic, David Locker, and Gordan Guyatt.
• Community Dental Health Services Research Unit, Faculty of Dentistry, University of Toronto, Toronto, Ontario, M5G 1G6, Canada. aleksandra.jokovic@utoronto.ca
• Health Qual Life Out. 2006 Jan 1;4:4.

BackgroundThe Child Perceptions Questionnaire for children aged 11 to 14 years (CPQ11-14) is a 37-item measure of oral-health-related quality of life (OHRQoL) encompassing four domains: oral symptoms, functional limitations, emotional and social well-being. To facilitate its use in clinical settings and population-based health surveys, it was shortened to 16 and 8 items. Item impact and stepwise regression methods were used to produce each version. This paper describes the developmental process, compares the discriminative properties of the resulting four short-forms and evaluates their precision relative to the original CPQ11-14.MethodsThe item impact method used data from the CPQ11-14 item reduction study to select the questions with the highest impact scores in each domain. The regression method, where the dependent variable was the overall CPQ11-14 score and the independent variables its individual questions, was applied to the data collected in the validity study for the CPQ11-14. The measurement properties (i.e. criterion validity, construct validity, internal consistency reliability and test-retest reliability) of all 4 short-forms were evaluated using the data from the validity and reliability studies for the CPQ11-14.ResultsAll short forms detected substantial variability in children's OHRQoL. The mean scores on the two 16-item questionnaires were almost identical, while on the two 8-item questionnaires they differed by only one score point. The mean scores standardized to 0-100 were higher on the short forms than the original CPQ11-14 (p < 0.001). There were strong significant correlations between all short-form scores and CPQ11-14 scores (0.87-0.98; p < 0.001). Hypotheses concerning construct validity were confirmed: the short-forms' scores were highest in the oro-facial, lower in the orthodontic and lowest in the paediatric dentistry group; all short-form questionnaires were positively correlated with the ratings of oral health and overall well-being, with the correlation coefficient being higher for the latter. The relative validity coefficients were 0.85 to 1.18. Cronbach's alpha and intraclass correlation coefficients ranged 0.71-0.83 and 0.71-0.77, respectively.ConclusionAll short forms demonstrated excellent criterion validity and good construct validity. The reliability coefficients exceeded standards for group-level comparisons. However, these are preliminary findings based on the convenience sampling and further testing in replicated studies involving clinical and general samples of children in various settings is necessary to establish measurement sensitivity and discriminative properties of these questionnaires.

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