Table 1. Association between serum HER 2 ECD levels and tissue HER 2 status (with different cut-off points).

	HER 2 status		Sensitivity (%)	Specifity (%)
	Positive	Negative	95% CI	95%CI
Cut-off point A			51.4(32.9–69.0)	96.2(85.58–97.19)
(15 ng/mL)
Elevated HER 2 ECD	19	7
Normal HER 2 ECD	18	175
P value (χ2 test)	<0.001
Cut-off point B			51.4(32.9–69.0)	97.3(88.33–98.38)
(16.35 ng/mL)
Elevated HER 2 ECD	19	5
Normal HER 2 ECD	18	177
P value (χ2 test)	<0.001
Cuto-ff point C			32.4(17.5–51.0)	100(96.31–100)
(22 ng/mL)
Elevated HER 2 ECD	12	0
Normal HER 2 ECD	25	182
P value (χ2 test)	<0.001