Which chemical test is used to detect ketone bodies in urine?

Appeared in: AIIMS CRE, SNO-2024

Explanation

The Nitroprusside test, also known as Rothera's test, is specifically designed to detect ketone bodies in urine.
It works on the principle that sodium nitroprusside reacts with acetoacetic acid and acetone in an alkaline medium to produce a characteristic purple-colored ring or complex.
This color change provides a qualitative or semi-quantitative measure of ketonuria, which is the presence of ketones in the urine.

Option A: This test detects the presence of reducing sugars, such as glucose, not ketone bodies. The reaction is based on the reduction of cupric ions to cuprous oxide.
Option C: This test is used to detect bilirubin (bile pigments) in the urine. The reagent oxidizes bilirubin to green biliverdin.
Option D: This test detects the presence of bile salts, not ketone bodies. It relies on a physical principle rather than a chemical reaction.

Visual 1: Chart: A summary table comparing common urine chemical tests (Nitroprusside, Benedict's, Fouchet's, Hay's), their target substances, and clinical significance.
Visual 2: Illustration: The color reaction of a positive Rothera's test, showing the purple ring formation at the interface of the liquids in a test tube.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Urine analysis for ketone bodies as background academic context rather than a clinical decision trigger.
Detecting ketonuria is crucial for diagnosing and managing diabetic ketoacidosis (DKA), a life-threatening emergency in patients with uncontrolled diabetes.
Nurses monitor for ketones in patients who are fasting, on ketogenic diets, or experiencing prolonged vomiting (e.g., hyperemesis gravidarum) to assess their metabolic state and risk for acidosis.
What if? If a patient's urine tests positive for both glucose (using a glucose oxidase strip) and ketones, it is a strong indicator of uncontrolled diabetes mellitus and requires immediate physician notification and intervention to prevent DKA.

How to Approach the Question

This is a factual recall question requiring knowledge of common laboratory tests.
First, identify the key substance in the question: 'ketone bodies'.
Next, review the options, which are all named chemical tests.
Recall or deduce the specific purpose of each test from your knowledge of clinical biochemistry.
Match 'ketone bodies' to the correct test. The Nitroprusside reaction is the classic and most specific test for ketones among the choices.

Concept Tested & Keywords

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E6 Biochemistry U Satyanarayana 7th Edition — Part 1 (pp 26-420 of 840) p. 464-840

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