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