What is the difference between diagnostic accuracy and clinical usefulness?

• A. Accuracy measures correct classification; usefulness considers impact on patient outcomes, costs, and feasibility in practice.
• B. They are identical concepts.
• C. Usefulness is only about cost.
• D. Accuracy is about cost.

Answer: (C)

Diagnostic accuracy is about how often a test correctly classifies people as having or not having a disease, using measures like sensitivity, specificity, and overall accuracy. Clinical usefulness goes beyond those numbers and asks whether using the test actually improves patient care in the real world, considering how results affect management, patient outcomes, potential harms from false results, costs, and how feasible it is to implement the test in practice. A test can be very accurate but of limited usefulness if it’s expensive or hard to use; or a test with moderate accuracy can be highly useful if it’s inexpensive, safe, rapid, and clearly guides better decisions. In short, accuracy = correctness of classification; usefulness = real-world impact on outcomes, costs, and feasibility.