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Sensitivity (Se): probability of a positive test given the individuals is diseased.

Se = # diseased individuals with a positive test/ # diseased individuals

Specificity (Sp): probability of a negative test given the individual is not diseased.

Sp =# non-diseased individuals with a negative test/ # non-diseased individuals

Positive predictive value (PPV): probability of disease given a positive test, influenced by population disease prevalence (pD).

PPV = true positives/true positives + false positives

PPV = (pD x Se/{pD x Se} + {[1-pD] x [1-Sp}}

Negative predictive value (NPV): probability of the absence of disease given a negative test, influenced by population disease prevalence.

NPV = true negatives/true negatives + false negatives

NPV = pD x {1-Se}/{pD x [1-Se]} + {[1-pD] x Sp}