When should you order a diagnostic test?

When should you order a diagnostic test?

• A. Only if it will change management
• B. Only if it improves diagnostic accuracy
• C. Only if it reduces cost
• D. Only if the pretest probability is high

Answer: (A)

The idea being tested is that a diagnostic test should be used only when its result will change what you do for the patient. If the test outcome wouldn’t lead you to change management—such as starting or stopping a treatment, ordering another test, or deciding on a procedure—then ordering it adds cost, time, and potential harm without improving care. That’s why the best answer is to order a diagnostic test only if it will change management. Even if a test could improve diagnostic accuracy, or seems cheaper, or the patient has a high pretest probability, those factors don’t justify testing unless the result will alter the plan of care. For example, you might avoid a test if you would treat the patient the same way regardless of the result, or avoid an invasive step if the decision would be the same with or without the test.

The idea being tested is that a diagnostic test should be used only when its result will change what you do for the patient. If the test outcome wouldn’t lead you to change management—such as starting or stopping a treatment, ordering another test, or deciding on a procedure—then ordering it adds cost, time, and potential harm without improving care.

That’s why the best answer is to order a diagnostic test only if it will change management. Even if a test could improve diagnostic accuracy, or seems cheaper, or the patient has a high pretest probability, those factors don’t justify testing unless the result will alter the plan of care. For example, you might avoid a test if you would treat the patient the same way regardless of the result, or avoid an invasive step if the decision would be the same with or without the test.