Validity assessment and determination of the cutoff value for the Index of Complexity, Outcome and Need among 12–13 year-olds in Southern Chinese

To validate the use of the Index of Complexity, Outcome and Need (ICON) in assessing orthodontic treatment need among 12–13 year-olds in southern China, we determined the threshold value of ICON based on Chinese orthodontists' judgments. The samples consisted of 335 students in grade 7 from 16 randomly selected middle schools in Chengdu, China. Three associate professors provided ICON scores for each participant and the results were compared with the gold standard judgments from 25 experts on treatment needs. Based on the gold standard, 195 casts belonged to the treatment category, while the rest 140 belonged to the no-treatment category. With the international cutoff point of 43, the sensitivity and specificity of the ICON score were 0.29 and 0.98. The best compromise between sensitivity and specificity in Chengdu, compared with the gold standard, was found at a cutoff point of 29, and the sensitivity and specificity were 0.88 and 0.83. When used to evaluate the treatment need of 12–13 year-olds in southern China, the international ICON cutoff value did not correspond well with Chinese orthodontists' judgments; a lower cutoff value of 29 offered a greater sensitivity and specificity with respect to expert orthodontists' perception of treatment need. Analysis of a popular orthodontics assessment tool shows that southern China requires a lower cutoff point than other regions. Using orthodontic data collected from 12–13-year-old students in southern China, Wen-li Lai and co-workers at Sichuan University, China, validated the Index of Complexity, Outcome and Need (ICON) — a computer program used to calculate the perceived severity of malocclusions (misaligned teeth) on a points scale and suggest a point at which treatment is necessary. The researchers compared the scores generated by ICON for the 335 students with individual scores given by 25 professional Chinese orthodontists. Lai and co-workers found that the current cutoff point of ICON used internationally is too high for this region, so they propose a lower cutoff point that is more in-line with the orthodontists' expert opinions.