Clinical biochemistry: pseudohyperkalaemia: 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: pseudohyperkalaemia

Sample item

A 35-year-old woman attending for a routine check-up has a serum potassium of 6.9 mmol/L. She is asymptomatic, her ECG is normal, renal function is normal and she takes no drugs. The laboratory notes the sample was haemolysed and arrived 5 hours after collection. What is the best next step?

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

The answer and the reasoning

B. Repeat the potassium on a fresh, promptly processed sample before treating

Haemolysis, delayed separation of serum and prolonged tourniquet use release potassium from cells and cause spurious hyperkalaemia, since intracellular potassium is about 150 mmol/L. When the ECG and renal function are normal and a cause is evident, the result should be repeated before acting. Plasma or whole-blood gas potassium helps, particularly in thrombocytosis or leucocytosis.

Option by option

  • A. Start haemodialysis

    Dialysis is for refractory hyperkalaemia with renal failure.

  • B. Repeat the potassium on a fresh, promptly processed sample before treating (correct)

    Correct. Verifying an implausible value avoids needless treatment.

  • C. Give a potassium-binding resin and a low-potassium diet only

    A resin and diet change are chronic measures that do not address the spurious sample.

  • D. Give intravenous calcium gluconate and insulin with dextrose

    Emergency treatment is for true hyperkalaemia with ECG changes, which is unlikely here.

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.

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Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is B, Repeat the potassium on a fresh, promptly processed sample before treating. Haemolysis, delayed separation of serum and prolonged tourniquet use release potassium from cells and cause spurious hyperkalaemia, since intracellular potassium is about 150 mmol/L.

Why is "Start haemodialysis" not the answer?

Dialysis is for refractory hyperkalaemia with renal failure.

Why is "Give a potassium-binding resin and a low-potassium diet only" not the answer?

A resin and diet change are chronic measures that do not address the spurious sample.

Why is "Give intravenous calcium gluconate and insulin with dextrose" not the answer?

Emergency treatment is for true hyperkalaemia with ECG changes, which is unlikely here.

What concept does this question test?

It tests Clinical biochemistry: pseudohyperkalaemia in Biochemistry. When the ECG and renal function are normal and a cause is evident, the result should be repeated before acting. Plasma or whole-blood gas potassium helps, particularly in thrombocytosis or leucocytosis.

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: pseudohyperkalaemia?

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.