How do screening and diagnostic tests vary?

• A. Screening tests are used to diagnose disease in sick animals
• B. Screening tests are used in healthy animals to detect prevalence and disease agents
• C. They have different evaluation principles
• D. Diagnostic tests confirm or classify disease

Answer: (B)

Screening tests are used in healthy animals to detect prevalence and disease agents. The point is to look for potential disease in individuals who don’t yet show symptoms, so you can gauge how common the disease or pathogen is in a population and flag cases for follow-up testing. Diagnostic tests, by contrast, are employed to confirm or classify disease in someone who is suspected of having the illness or who has a positive screening result. So the best choice highlights the distinct use of screening in apparently healthy populations to assess presence or spread of disease, while diagnostic testing serves to confirm the diagnosis in individuals.