A comparison of the reliability and validity of 3 occlusal indexes of orthodontic treatment need

Several occlusal indexes are currently used to ascertain eligibility for or thodontic treatment. A comparison of 3 indexes of orthodontic treatment nee d was made with the consensus opinion of a panel of 15 experienced orthodon tists. Sets of study casts (170) representing the full spectrum of malocclu sions were selected. An examiner, calibrated in the Dental Aesthetic Index, the Handicapping Labiolingual Deviation with the California Modification, and the Index of Orthodontic Treatment Need, scored the casts. The panel of orthodontists individually rated the same casts for their degree of orthod ontic treatment need. The mean rating of the panel on the need for treatmen t was used as the gold standard for evaluating the validity of the indexes. Intrarater and interrater reliability was high (kappa > 0.8). Overall accu racy of the indexes, as reflected in area under receiver-operating characte ristic curves, was also high: Dental Aesthetic Index, 95%; Handicapping Lab iolingual Deviation with the California Modification, 94%; and Index of Ort hodontic Treatment Need, 98%. Cutoff points for the indexes that resulted i n the closest agreement with the gold standard differed from the published cutoff points for the indexes. The indexes appear to be valid measures of t reatment need as perceived by orthodontists. The published cutoff points fo r the indexes were more conservative in assigning patients for treatment th an a panel of orthodontists. However, adjusting the cutoff points moved all 3 indexes into close agreement with the experts.