Gregg-Graniteville Library: Public Health: Screening Tests

What Makes a Good Screening Test?

A screening test checks for diseases or conditions before symptoms appear, in an effort to find diseases early when they may be easier to treat or cure.

Fundamentals of Screening:

The disease must have a great enough burden of suffering to make going through the screening worth it.
A screening test must be able to find disease earlier than you would without the screening test.
There must a therapy or treatment that will lead to the patient having a better outcome.
Disorders show should have a low prevalence and be relatively rare.

Must screen a large number of people.
Most screening test are going to have a good number of false positives.
Screening risks should be rare but apply to everyone.
Only a few will benefit from screening.

Sensitivity

Sensitivity and specificity describe how accurate a test is.

Sensitivity is a measure of how reliable a test is in identifying the presence of a condition. It measures how often a test will detect the presence of a disease in people who have the disease (true positives).

Specificity

Specificity is a measure of how often a test will detect the absence of a disease in those who do not have the disease (true negatives).

Positive Predictive Value

Predictive value describes the likelihood that a person has or does not have the condition based on the results of the test. The more prevalent the disease, the higher the PPV and the lower the NPV.

Positive Predictive Value (PPV) is the likelihood that a person with a positive test result truly has the disease.