Table 1.

Calculation of Sensitivity and Specificity depending on ECAD expression ("2x2 table").

		"gold standard" = result of sentinel node biopsy
		occult metastatic disease: Yes	occult metastatic disease: No
new predictive marker for occult metastatic disease (ECAD)	Low ECAD	true positive	false positive	all test positives
	expression	a	b	a + b
	High ECAD	c	d	all test
	expression	false negative	true negative	negatives
				c + d
		a + c	b + d
		all with occult	all without occult
		disease	disease

Hypothesis: low ECAD expression (test) predicts occult metastatic disease

sensitivity: a/(a + c)

specificity: d/(b + d)