This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Beta oxidation of fatty acids, Subject name: Biochemistry
Ketone body that cannot be detected by Rothera's test: 
Select and explain. 
A. Acetoacetate, B. Acetone, C. Beta hydroxy butyrate, D. All the above can be detected
C: Beta hydroxy butyrate
Answer: C: Beta hydroxy butyrate 
Explanation: Rothera's test can only detect acetoacetate and acetone, and not beta-hydroxy butyrate. Rothera's test: Ketone bodies react with sodium nitroprusside (in the presence of NH3) to form a purple colored ring. Positive test indicate Acetoacetate and Acetone. No specific test available for beta-hydroxy butyrate. So, it is first oxidised to Acetoacetate, then Rothera's test is performed.