TABLE 1.

Definition and calculation of statistical measures used to express diagnostic test utility

Statistical measure	Definition	Calculation
Accuracy	The proportion of people who were correctly identified as either having or not having the disease or dysfunction	(TP + TN) / (TP + FP + FN + TN)
Sensitivity	The proportion of people who have the disease or dysfunction who test positive	TP / (TP + FN)
Specificity	The proportion of people who do not have the disease or dysfunction who test negative	TN / (FP + TN)
Positive predictive value	The proportion of people who test positive and who have the disease or dysfunction	TP / (TP + FP)
Negative predictive value	The proportion of people who test negative and who do not have the disease or dysfunction	TN / (FN + TN)
Positive likelihood ratio	How likely a positive test result is in people who have the disease or dysfunction as compared to how likely it is in those who do not have the disease or dysfunction)	Sensitivity/(1-specificity)
Negative likelihood ratio	How likely a negative test result is in people who have the disease or dysfunction as compared to how likely it is in those who do not have the disease or dysfunction	(1-sensitivity)/specificity

TP= true positive; TN= true negative; FP= false positive; FN= false negative