Test characteristics of rasterstereography for the early diagnosis of adolescent idiopathic scoliosis

This study aimed to evaluate rasterstereography of the spine as a diagnostic test for adolescent idiopathic soliosis (AIS), and to compare its results with those obtained using a scoliometer. Adolescents suspected of AIS and scheduled for radiographs were included. Rasterstereographic scoliosis angle (SA), maximal vertebral surface rotation (ROT), and angle of trunk rotation (ATR) with a scoliometer were evaluated. The area under the curve (AUC) from receiver operating characteristic (ROC) plots were used to describe the discriminative ability of the SA, ROT, and ATR for scoliosis, defined as a Cobb angle > 10°. Test characteristics (sensitivity and specificity) were reported for the best threshold identified using the Youden method. AUC of SA, ATR, and ROT were compared using the bootstrap test for two correlated ROC curves method. Of 212 patients studied, 146 (69%) had an AIS. The AUC was 0.74 for scoliosis angle (threshold 12.5°, sensitivity 75%, specificity 65%), 0.65 for maximal vertebral surface rotation (threshold 7.5°, sensitivity 63%, specificity 64%), and 0.82 for angle of trunk rotation (threshold 5.5°, sensitivity 65%, specificity 80%). The AUC of ROT was significantly lower than that of ATR (p < 0.001) and SA (p < 0.001). The AUCs of ATR and SA were not significantly different (p = 0.115). The rasterstereographic scoliosis angle has better diagnostic characteristics than the angle of trunk rotation evaluated with a scoliometer, with similar AUCs and a higher sensitivity.