Table 3:

Diagnostic performance of MR imaging after grouping of grades into benign or malignant according to grades in the current, modified, and plain scan grading systems

MR Imaging Grade Grouping to Indicate NPC	FP	FN	TP	TN	Sen %	Spec %	PPV %	NPV %	Accuracy %
Grades in the current system
Primary tumor 3, 4^{^a}	140	1	382	243	99.74	63.45	73.18	99.59	81.59
Primary tumor only 4	8	48	335	375	87.47	97.91	97.67	88.65	92.69
Grades in the modified system
Primary tumor 3, 4, 5	140	1	382	243	99.74	63.45	73.18	99.59	81.59
Primary tumor 4, 5	31	14	369	352	96.34	91.91	92.25	96.17	94.13
Primary tumor 4, 5 + node 5^{^a}	40	8	375	343	97.91	89.56	90.36	97.72	93.73
Grades in the plain scan system
Primary tumor 4, 5	45	17	366	338	95.56	88.25	89.05	95.21	91.91
Primary tumor 4, 5 + node 5^{^a}	52	9	374	331	97.65	86.42	87.79	97.35	92.04

Note:—FP indicates false-positive; FN, false-negative; TP, true-positive; TN, true-negative; Sen, sensitivity; Spec, specificity; PPV, positive predictive value; NPV, negative predictive value.
↵a Combination of grades in the respective current, modified, and plain scan systems in Table 2.