Validity of the Index of Complexity, Outcome, and Need (ICON) in determining orthodontic treatment need.

Occlusal indices are used to determine eligibility for orthodontic treatment in several publicly funded programs. The Index of Complexity, Outcome, and Need (ICON), based on the perception of 97 orthodontists from 9 countries, has been proposed as a multipurpose occlusal index. The aim of this study was to investigate the validity of the ICON as an index of orthodontic treatment need compared with the perception of need as determined by a panel of US orthodontists. One hundred seventy study casts, representing a full spectrum of malocclusion types and severity, were scored for orthodontic treatment need by an examiner calibrated in the ICON. The results were compared with the decisions of an expert panel of 15 orthodontic specialists from the central Ohio area. The simple kappa statistic (0.81) indicated very high agreement of the index with the decisions of the expert panel. The sensitivity (94%), specificity (85%), positive predictive value (92%), negative predictive value (90%), and overall accuracy of the ICON (91%) also confirmed good agreement with the orthodontic specialists. The panel found that 64% of the casts required orthodontic treatment; the ICON scores indicated that 65% of the cases needed treatment. There was agreement between the expert panel and the index in 155 of the 170 cases. These results support the use of the ICON as a validated index of orthodontic treatment need.