ROC curve with day 15 iNKT/T ratio. Day 15 iNKT/T ratio can discriminate the risk of aGVHD (AUC = 0.812). An AUC of 1.0 indicates perfect discrimination, whereas an area of 0.5 indicates that the test discriminates no better than chance. An iNKT/T cut-off ratio equal to 0.58 × 10⁻³ at day 15 yields the best balance between specificity and sensitivity (87.9% true-positive rate and 30.5% false-positive rate).