Table 3.

Diagnostic performance matrix (A) and outcomes (B) on the internal validation, and test after training with all dataset (phase 2). Optimal cut off value was estimated when it is located on the highest Youden index in the internal validation

(1) Internal validation with Hospital A and B set, (2) Test after training and internal validation with Hospital A and B set. Pos positive, fracture of femoral neck; Neg negative, no fracture. AUC under the curve of the receiver operating characteristic curve (ROC). Accuracy, the fraction of the correct predictions over the total predictions. The Youden index; the sensitivity + specificity – 1 that is the vertical distance between the 45° line and the point on ROC curve. Sen sensitivity, Spe specificity. In the internal and external validation, we selected the optimal cutoff value when the Youden index value is highest in the test after training with Hospital A set. CI confidence interval. E, easy cases subclassified to garden III or IV types. D, difficult cases subclassified to garden I or II types. *p < 0.05 is statistically significant