Insights into Imaging

Table 4 Performance of mrPSM grading systems in the derivation and validation groups

From: An MRI-based grading system for preoperative risk estimation of positive surgical margin after radical prostatectomy

	Derivation group		Validation group			p values
Grading systems	mrPSM1	mrPSM2	mrPSM1	mrPSM2	Park et al.’s system	mrPSM1 vs. Park et al	mrPSM2 vs. Park et al
Low risk (%)^a,b	17.4 (15/86)	16.7 (14/84)	25.0 (14/56)	24.1 (13/54)	17.9 (5/28)	-	-
Intermediate risk (%)^a,b	37.5 (12/32)	31.8 (7/22)	47.6 (10/21)	40.0 (6/15)	42.6 (20/47)	-	-
High risk (%)^a,b	65.2 (15/23)	60.0 (21/35)	72.7 (8/11)	68.4 (13/19)	53.8 (7/13)	-	-
AUC	0.705 (0.614–0.795)	0.713 (0.624–0.802)	0.672 (0.565–0.780)	0.686 (0.577–0.794)	0.646 (0.542–0.751)	0.566	0.395
Cut-off value	≥ 2	≥ 2	≥ 2	≥ 2	≥ 2	-	-
Accuracy	0.695 (0.692–0.698)	0.695 (0.692–0.698)	0.682 (0.677–0.687)	0.682 (0.677–0.687)	0.568 (0.563–0.574)	0.089	0.078
Sensitivity	0.643 (0.498–0.788)	0.667 (0.524–0.809)	0.562 (0.391–0.734)	0.594 (0.424–0.764)	0.844 (0.718–0.970)	0.008	0.013
Specificity	0.717 (0.628–0.806)	0.707 (0.617–0.797)	0.750 (0.637–0.863)	0.732 (0.616–0.848)	0.411 (0.282–0.540)	< 0.001	< 0.001
PPV	0.491 (0.359–0.623)	0.491 (0.361–0.621)	0.562 (0.391–0.734)	0.559 (0.392–0.726)	0.450 (0.324–0.576)	-	-
NPV	0.826 (0.745–0.906)	0.833 (0.754–0.913)	0.750 (0.637–0.863)	0.759 (0.645–0.873)	0.821 (0.680–0.963)	-	-

AUC area under the receiver operating characteristic curve, PPV positive predictive value, NPV negative predictive value, mrPSM1 the first MRI-based grading system for positive surgical margin, mrPSM1 the second MRI-based grading system for positive surgical margin
^aData are the percentage of PSM
^bFor mrPSM1 and mrPSM2, patients who were classified into grade 1, grade 2, and grade 3 were considered to have low, intermediate, and high risk of PSM, respectively; for Park et al.’s system, patients with risk score of 0–2, 3–5, and 6–7 were considered to have low, intermediate, and high risk of PSM, respectively

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