Screening tests look for possible disease or risk in people who feel well, while diagnostic tests confirm whether a disease is actually present, usually in people with symptoms or an abnormal screen.

Purpose

• Screening tests aim to pick up early signs of disease or increased risk so that problems can be found and treated sooner.

• Diagnostic tests aim to establish a definite “yes or no” diagnosis to guide treatment decisions.

Who gets each test

• Screening is offered to large groups of people who do not have symptoms but may be at risk because of age, sex, or other factors (for example, routine blood pressure checks or screening mammograms).

• Diagnostic testing is done for people who have symptoms, or who had an abnormal screening result and now need confirmation.

How the tests are designed

• Screening tests are usually simple, quick, less invasive, and set to be very sensitive so they miss as few potential cases as possible, even if that means more false alarms.

• Diagnostic tests can be more complex, invasive, and costly, and are designed to be highly accurate and specific so that a positive result strongly indicates true disease.

What the results mean

• A positive screening result means “higher risk” or “suspicious, needs further testing,” not a definite diagnosis.

• A positive diagnostic test result is intended to confirm that the disease is present (and a negative result to confirm it is absent), guiding treatment or follow‑up.