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

Of the 12-year-olds, 23.5 per cent (n = 121) and of the 15- to 16-year-olds, 26.6 per cent (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 per cent and Kappa for diagnostic agreement was 0.52 [95 per cent confidence interval (CI): 0.42-0.63]. For the 15- to 16-year-olds (n = 292), the figures were 82.5 per cent and 0.38 (95 per cent CI: 0.24-0.52), respectively. For the total sample (n = 655), the observed agreement was 83 per cent and the diagnostic agreement was 0.47 (95 per cent 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 per cent 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.