Validation of the American Board of Orthodontics Objective Grading System for assessing the treatment outcomes of Chinese patients.

INTRODUCTION Orthodontics in China has developed rapidly, but there is no standard index of treatment outcomes. We assessed the validity of the American Board of Orthodontics Objective Grading System (ABO-OGS) for the classification of treatment outcomes in Chinese patients. METHODS We randomly selected 108 patients who completed treatment between July 2005 and September 2008 in 6 orthodontic treatment centers across China. Sixty-nine experienced Chinese orthodontists made subjective assessments of the end-of-treatment casts for each patient. Three examiners then used the ABO-OGS to measure the casts. Pearson correlation analysis and receiver operating characteristic curve analysis were conducted to evaluate the correspondence between the ABO-OGS cast measurements and the orthodontists' subjective assessments. RESULTS The average subjective grading scores were highly correlated with the ABO-OGS scores (r = 0.7042). Four of the 7 study cast components of the ABO-OGS score-occlusal relationship, overjet, interproximal contact, and alignment-were statistically significantly correlated with the judges' subjective assessments. Together, these 4 accounted for 58% of the variability in the average subjective grading scores. The ABO-OGS cutoff score for cases that the judges deemed satisfactory was 16 points; the corresponding cutoff score for cases that the judges considered acceptable was 21 points. CONCLUSIONS The ABO-OGS is a valid index for the assessment of treatment outcomes in Chinese patients. By comparing the objective scores on this modification of the ABO-OGS with the mean subjective assessment of a panel of highly qualified Chinese orthodontists, a cutoff point for satisfactory treatment outcome was defined as 16 points or fewer, with scores of 16 to 21 points denoting less than satisfactory but still acceptable treatment. Cases that scored greater than 21 points were considered unacceptable.