Table 5.

Two-way contingency table analysis showing predictive accuracy of the nomogram.

		Training set			Validation set
		Observed (N)			Observed (N)
		LN ≥ 3	LN ≤ 2	Total	LN ≥ 3	LN ≤ 2	Total
Expected (N)	LN ≥ 3	45	81	126	27	38	65
	LN ≤ 2	37	672	709	16	591	607
	Total	82	753	835	43	629	672
Accuracy % (95% CI)		85.8 (0.83–0.88)			90.9 (0.89–0.93)
Sensitivity % (95% CI)		54.9 (0.44–0.65)			59.5 (0.45–0.74)
Specificity % (95% CI)		89.2 (0.87–0.91)			93.0 (0.91–0.95)
PPV % (95% CI)		35.7 (0.29–0.42)			36.2 (0.28–0.45)
NPV % (95% CI)		94.7 (0.94–0.96)			97.2 (0.96–0.98)

LN, Lymph node; PPV, Positive predictive value; NPV, Negative predictive value; CI, Confidence interval.