Consistency in measuring OHRQoL across gender using structural equation modeling

Background: The Child Perceptions Questionnaire (CPQ) was developed in Toronto as a measure of the oral health-related quality of life (OHRQoL) for children. The short form with 8 items (RSF:8) of CPQ was also derived.

Objectives: To investigate the consistency of RSF:8 in measuring OHRQoL between boys and girls in Hong Kong at age 12 and 15 years.

Methods: The instrument was administered to 504 children aged 12 years (boys: 292; girls: 212) and re-administered to the same group of children at the age of 15 years three years later (total: 424; boys: 233; girls: 191). Structural Equation Modeling (SEM) approach was used to assess the goodness-of fit of the measurement models of RSF: 8 in measuring OHRQoL for boys and girls separately at baseline and three years after. The consistency (measurement invariance) of RSF:8 in measuring OHRQoL between boys and girls were then tested separately at age 12 and 15 years. To test for the measurement invariance (configural structure, factor loadings, error variances, factor variances and covariances), a series of hierarchically nested models were tested by the chi-square difference tests and the more restricted model would be accepted if the chi-square difference test was not significant (p > 0.05).

Results: Measurement models separately for boys and girls fitted the data well. When testing for the measurement invariance between boys and girls aged 12 and 15 years separately, the models constrained with invariant configural structure, factor loadings, error variances, factor variances and covariances were accepted (p>0.05).

Conclusion: This study indicated that RSF:8 measured OHRQoL for children in Hong Kong consistently across gender at age 12 and 15 years.

Supported by a grant from the Research Grants Council of the Hong Kong SAR, China (Project No. HKU 778907M).