Validation of the complexity and treatment outcome components of the index of complexity, outcome, and need (ICON).

Occlusal indexes objectively quantify malocclusions. The index of complexity, outcome and treatment need (ICON) is a new index developed to measure several aspects of occlusion and treatment outcome. The purpose of this study was to test the validity of the ICON in measuring orthodontic complexity, outcome, and degree of improvement. Fifteen orthodontists evaluated 100 pairs of pretreatment and posttreatment study models for complexity, outcome, and degree of improvement. A calibrated examiner used ICON to score the casts. One month later, a random subset of 40 study casts was rescored by raters and the examiner for reliability testing. A simple kappa statistic was used to assess agreement between the scores from the expert panel and from the ICON examiner. Interrater agreement was moderate for complexity (kappa =.50), slight for outcome (kappa =.18), and poor for degree of improvement (kappa =.04). Reliability of the calibrated examiner was kappa =.90 for pretreatment and kappa =.83 for posttreatment casts. Agreement between the raters and the ICON scores was moderate for complexity (kappa =.52) and outcome (kappa =.50) and fair for degree of improvement (kappa =.27). ICON is valid for assessing cases for complexity and outcome. However, lack of agreement among the raters for degree of improvement and between the ICON-based evaluations and the orthodontists' evaluation of degree of improvement suggests that this component should be reexamined.