Table 1.

	Control
Test	Positive	Negative	Total
Positive	a	b	a + b
Negative	c	d	c + d
Total	a + c	b + d	N

Sensitivity: a/(a + c)

Specificity: d/(b + d)

Positive predictive value (PPV): a/(a + b)

Negative predictive value (NPV): d/(c + d)