Which ketone body is primarily detected by the nitroprusside urine test?

• A. Acetoacetate
• B. 3-hydroxybutyrate
• C. Acetone
• D. All three

Answer: (A)

The test detects acetoacetate as the ketone it reacts with most reliably under alkaline conditions to form a colored product with nitroprusside. Acetone can give a weak reaction, but 3-hydroxybutyrate does not react with nitroprusside, so it is not detected by this test. Therefore, the nitroprusside urine test is best described as primarily detecting acetoacetate.