Gold standard		Total
	S+	S−
Clinical Test
T+	a=True Positive	b=False Positive	a+b
T	c=FalseNegative	d=True Negative	c+d
Total	a+c	b+d

Sensitivity=a/a+c, Specificity=d/b+d, Positive Predictive Value (PPV) = a/a+b, Negative Predictive Value (NPV) = d/c+d