Genotype or disease		A: True positives	C: False negative
	Present	Absent	B: False positives	D: True negative
Test
Positive	A	B	Sensitivity: Specificity:	A/(A + C) D/(D + B)
Negative	C	D	Positive predictive value:	A/(A + B)
			Negative predictive value:	D/(C + D)