Diagnostic agreement in the assessment of orthodontic treatment need using the Dental Aesthetic Index and the Index of Orthodontic Treatment Need.

The aim of this study was to estimate the diagnostic agreement between assessments of orthodontic treatment need of a child population using the Dental Aesthetic Index (DAI) and the Index of Orthodontic Treatment Need (IOTN). A cross-sectional study of a representative random sample of children aged 12 (n = 475) and 15-16 (n = 398) years was carried out in the Valencia region of Spain. A Student's t-test was used to compare the DAI means by gender and age and a chi-square test to compare the proportions of the population in need of orthodontic treatment. To calculate the agreement between the two indices, intra-class correlation coefficient and Kappa statistics were employed. Of the 12-year-olds, 23.5 percent (n = 121) and of the 15- to 16-year-olds, 26.6 percent (n = 108) were receiving or had previously received orthodontic treatment. The observed agreement between the two indices on the need for treatment among the 12-year-olds (n = 363) was 83.4 percent and Kappa for diagnostic agreement was 0.52 [95 percent confidence interval (CI): 0.42-0.63]. For the 15- to 16-year-olds (n = 292), the figures were 82.5 percent and 0.38 (95 percent CI: 0.24-0.52), respectively. For the total sample (n = 655), the observed agreement was 83 percent and the diagnostic agreement was 0.47 (95 percent CI: 0.39-0.55). For this population, there was only moderate agreement between the two indices. This means that, when one of these indices is used to measure or prioritize orthodontic treatment in a determined population, the individuals selected with an obvious treatment need are going to be different in 17 percent of the cases depending on which index is used, DAI or IOTN. This difference has to be taken in consideration when measuring, recording, or quantifying orthodontic treatment need.