What factors should govern the selection and use of a screening instrument by a health clinic? how does the predictive value of a screening test vary according to the prevalence of?

Screening includes the testing of individuals without a known disorder. This is done to find that if the people possess the disorder. The early identification of the disorder signifies early treatment. The selection and use of a screening instrument by a health clinic are dependent upon its validity and reliability.

When the prevalence of a disease reduces, the predictive value (+) falls, and the predictive value (-) elevates. The predictive value (+) signifies the ratio of true positives who actually possesses the disease among all those with positive test results.

On the other hand, the predictive value (-) signifies towards the ratio of true negatives who actually do not possess the disease among all those with negative test results.