Which statement about nitroprusside testing for ketones is true?

• A. Nitroprusside test detects acetoacetate and is highly sensitive for beta-hydroxybutyrate.
• B. Nitroprusside test detects acetoacetate, and is less sensitive for beta-hydroxybutyrate.
• C. Nitroprusside test detects beta-hydroxybutyrate only.
• D. Nitroprusside test detects acetone.

Answer: (B)

Nitroprusside testing detects ketone bodies through a color-forming reaction that responds specifically to acetoacetate (and, to some extent, acetone via its equilibrium with acetoacetate). Beta-hydroxybutyrate does not react strongly with the nitroprusside reagent, so the test does not reliably pick it up. That makes the test very good at indicating acetoacetate presence, while being less sensitive for beta-hydroxybutyrate. In clinical terms, this is why the test can be negative or weak when ketosis is driven mainly by beta-hydroxybutyrate, even though ketones are elevated.