What is the difference between a diagnostic test and a screening test?

A diagnostic test is completed to either diagnose or rule out a specific health condition. The results of diagnostic tests alone provide enough confidence for a healthcare provider to diagnose and make treatment determinations. 

A screening test is done to help determine a risk for a specific health condition. The results of screening tests alone cannot be used to confirm or rule out a particular diagnosis. If positive, the results are to be used in combination with symptoms, medical and family history, and additional testing as needed to aid in diagnosing or ruling out a disease. 

The Celiac Disease Screening Test checks for antibodies that, when present or elevated, may indicate celiac disease. This is intended to be a first step in the process of determining if you have celiac disease. Positive results are not a diagnosis of celiac disease but may mean you need further evaluation and additional testing, which might include an endoscopy.