Template:SensSpecPPVNPV


 * Relationships among terms:


 * A worked example: The fecal occult blood (FOB) screen test was used in 2030 people to look for bowel cancer:

Related calculations
 * False positive rate (α) = FP / (FP + TN) = 180 / (180 + 1820) = 9% = 1 − specificity
 * False negative rate (β) = FN / (TP + FN) = 10 / (20 + 10) = 33% = 1 − sensitivity
 * Power = sensitivity = 1 − β
 * Likelihood ratio positive = sensitivity / (1 &minus; specificity) = 66.67% / (1 &minus; 91%) = 7.4
 * Likelihood ratio negative = (1 &minus; sensitivity) / specificity = (1 &minus; 66.67%) / 91% = 0.37

Hence with large numbers of false positives and few false negatives, a positive FOB screen test is in itself poor at confirming cancer (PPV = 10%) and further investigations must be undertaken; it did, however, correctly identify 66.7% of all cancers (the sensitivity). However as a screening test, a negative result is very good at reassuring that a patient does not have cancer (NPV = 99.5%) and at this initial screen correctly identifies 91% of those who do not have cancer (the specificity).

Note: This template is used as a portion of the articles on sensitivity, specificity, likelihood ratios in diagnostic testing, etc. See those articles for additional citations.