Table 2.

ALN metastasis state of 567 patients detected by SLNB

SLN status	ALN status		Total
	(+)	(–)
(+)	172 (a)	0 (c)	172
(–)	19 (b)	376 (d)	395
Total	191	376	567

For SLNB, the FNR was $\left(\mathrm{b}\right)/\left(\mathrm{a}+\mathrm{b}\right)=19\left(172+19\right)=9.9\%$. Sensitivity was $\left(\mathrm{a}\right)\left./(\mathrm{a}+\mathrm{b}\right)=172\left(172+19\right)=90.1\%$. Accuracy rate was $\left(\text{a}+\text{d}\right)/\left(\text{a + b}+\text{c}+\text{d}\right)=\left(172\text{+ 376}\right)/\left(172+19+0+376\right)=96.6\%$. Negative predictive value was $\left(\text{d}\right)/\left(\text{b}+\text{d}\right)=376/\left(19+376\right)=95.2\%$

Abbreviations: ALN axillary lymph node, SLNB sentinel lymph node biopsy, SLN sentinel lymph node, FNR false-negative rate