title: Assessing consistency in oral health-related quality of life (OHRQoL) across gender and stability of OHRQoL over time for adolescents using Structural Equation Modeling.
abstract: BACKGROUND
  The Child Perceptions Questionnaire for children aged 11-14 years (CPQ(11-14) ) was developed in Toronto as a measure of the oral health-related quality of life (OHRQoL) for children/adolescents. The short form with eight items (RSF:8) was also derived.
  
  
  OBJECTIVE
  (i) To investigate the consistency of RSF:8 in measuring the OHRQoL between boys and girls, (ii) to investigate the measurement invariance and stability of RSF:8 in measuring OHRQoL for Hong Kong adolescents over time, and (iii) to determine the latent mean differences across gender and over time.
  
  
  METHODS
  The instrument was administered to 542 adolescents aged 12 years and re-administered to the same group of adolescents 3 years later. Structural Equation Modeling (SEM) was used to test the measurement invariance at different levels. A series of hierarchically nested models (configural structure, factor loadings, error variances, factor variances and covariance, intercept invariance) were tested by the chi-square difference tests, and the more restricted model would be accepted if the chi-square difference test was insignificant (P > 0.05). The latent means would be estimated if intercept invariance was not accepted. The stability of OHRQoL over time was investigated by computing the stability coefficients.
  
  
  RESULTS
  For multiple group analysis, the model with the level of invariance up to factor variances and covariance was accepted (P > 0.05). The latent mean of girls was significantly lower (indicating better OHRQoL) than boys in social well-being (SWB). For panel data analysis, the model with the level of invariance up to factor variances and covariance was accepted (P > 0.05). The latent mean of the four domains decreased significantly (indicating improved OHRQoL) for adolescents aged 12-15 years. The stability coefficients ranged from 0.14 to 0.73 which demonstrated moderate stability except functional limitation (FL) with a relatively low stability.
  
  
  CONCLUSIONS
  This study indicated that RSF:8 measured OHRQoL for adolescents in Hong Kong consistently across gender. The OHRQoL in SWB for girls was better than boys. Also, the OHRQoL for adolescents was in the same factor structure with moderate stability and improved significantly over time.
authors.affiliation: Dental Public Health, Faculty of Dentistry Department of Statistics and Actuarial Science, University of Hong Kong, Hong Kong, China. mcmwong@hkucc.hku.hk
authors.forename: May C M
authors.initials: MC
authors.lastname: Wong
authors.forename: Abby W H
authors.initials: AW
authors.lastname: Lau
authors.forename: K F
authors.initials: KF
authors.lastname: Lam
authors.forename: Colman
authors.initials: C
authors.lastname: McGrath
authors.forename: Hai-Xia
authors.initials: HX
authors.lastname: Lu
mesh_terms: D000293:Adolescent; D002648:Child; D003753:Dental Health Surveys / Q000592:standards*; D005260:Female; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D008297:Male; D015233:Models, Statistical; D009909:Oral Health; D011788:Quality of Life; D015203:Reproducibility of Results; D012737:Sex Factors