Clinical biochemistry: alcoholic ketoacidosis: practice question

A Biochemistry question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Biochemistry · Clinical biochemistry: alcoholic ketoacidosis

Sample item

A chronic drinker who binged and then vomited and did not eat for 2 days has Kussmaul breathing, glucose 70 mg/dL, pH 7.20 and a high anion gap. The urine nitroprusside test is only weakly positive despite severe ketosis. What is the explanation?

ALow insulin levels suppress ketone productionBAcetone excretion by the lungs masks the reactionCEthanol is metabolised directly to acetoacetateDA high NADH to NAD ratio converts acetoacetate to a ketone the test misses

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. A high NADH to NAD ratio converts acetoacetate to a ketone the test misses

Ethanol metabolism raises the cytosolic and mitochondrial NADH to NAD ratio, shifting acetoacetate to beta-hydroxybutyrate, which the nitroprusside reaction does not detect. Measuring blood beta-hydroxybutyrate avoids the error. Treatment is dextrose, thiamine and fluids.

Option by option

A. Low insulin levels suppress ketone production
Insulin is low in this setting, which promotes rather than suppresses ketogenesis.
B. Acetone excretion by the lungs masks the reaction
Acetone loss by the lungs does not explain a weak urine reaction.
C. Ethanol is metabolised directly to acetoacetate
Ethanol is converted to acetaldehyde and acetate, not to acetoacetate.
D. A high NADH to NAD ratio converts acetoacetate to a ketone the test misses (correct)
Correct. Beta-hydroxybutyrate predominates and is not detected by nitroprusside.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is D, A high NADH to NAD ratio converts acetoacetate to a ketone the test misses. Ethanol metabolism raises the cytosolic and mitochondrial NADH to NAD ratio, shifting acetoacetate to beta-hydroxybutyrate, which the nitroprusside reaction does not detect.

Why is "Low insulin levels suppress ketone production" not the answer?

Insulin is low in this setting, which promotes rather than suppresses ketogenesis.

Why is "Acetone excretion by the lungs masks the reaction" not the answer?

Acetone loss by the lungs does not explain a weak urine reaction.

Why is "Ethanol is metabolised directly to acetoacetate" not the answer?

Ethanol is converted to acetaldehyde and acetate, not to acetoacetate.

What concept does this question test?

It tests Clinical biochemistry: alcoholic ketoacidosis in Biochemistry. Measuring blood beta-hydroxybutyrate avoids the error. Treatment is dextrose, thiamine and fluids.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Clinical biochemistry: alcoholic ketoacidosis?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.