Electrolytes: albumin-corrected calcium: practice question

A General Medicine 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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General Medicine · Electrolytes: albumin-corrected calcium

Sample item

A 55-year-old man with cirrhosis has no symptoms. Serum total calcium is 7.6 mg/dL with serum albumin 2.0 g/dL. Using the standard correction of 0.8 mg/dL for every 1 g/dL fall in albumin below 4.0 g/dL, what is his corrected calcium and the appropriate action?

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

The answer and the reasoning

A. Corrected 9.2 mg/dL, which is normal, so no calcium replacement is needed

Corrected calcium = measured calcium + 0.8 x (4.0 minus albumin) = 7.6 + 0.8 x 2.0 = 7.6 + 1.6 = 9.2 mg/dL, which is within the normal range of 8.5 to 10.5. Low albumin reduces the protein-bound fraction but the physiologically active ionised fraction is unchanged. If doubt persists, measure ionised calcium directly.

Option by option

  • A. Corrected 9.2 mg/dL, which is normal, so no calcium replacement is needed (correct)

    Correct. Adjusting for the low albumin brings the calcium into the normal range.

  • B. Corrected 10.8 mg/dL, so treat hypercalcaemia with saline

    Adding a correction of 1.6 per g/dL overshoots; the value is 9.2 and there is no hypercalcaemia.

  • C. Corrected 8.4 mg/dL, so start oral calcium supplements

    Correcting for only 1 g/dL of the albumin deficit underestimates the adjustment; the right result is 9.2.

  • D. Corrected 6.0 mg/dL, so give intravenous calcium gluconate

    Subtracting the correction instead of adding it gives an impossible figure of 6.0 and leads to unnecessary intravenous therapy.

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 General Medicine question

What is the answer to this General Medicine question?

The best answer is A, Corrected 9.2 mg/dL, which is normal, so no calcium replacement is needed. Corrected calcium = measured calcium + 0.

Why is "Corrected 10.8 mg/dL, so treat hypercalcaemia with saline" not the answer?

Adding a correction of 1.6 per g/dL overshoots; the value is 9.2 and there is no hypercalcaemia.

Why is "Corrected 8.4 mg/dL, so start oral calcium supplements" not the answer?

Correcting for only 1 g/dL of the albumin deficit underestimates the adjustment; the right result is 9.2.

Why is "Corrected 6.0 mg/dL, so give intravenous calcium gluconate" not the answer?

Subtracting the correction instead of adding it gives an impossible figure of 6.0 and leads to unnecessary intravenous therapy.

What concept does this question test?

It tests Electrolytes: albumin-corrected calcium in General Medicine. 8 x (4.0 minus albumin) = 7.6 + 0.8 x 2.0 = 7.6 + 1.6 = 9.2 mg/dL, which is within the normal range of 8.5 to 10.5. Low albumin reduces the protein-bound fraction but the physiologically active ionised fraction is unchanged. If doubt persists, measure ionised calcium directly.

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 Electrolytes: albumin-corrected calcium?

For each disease know the classic presentation, the best test, and the first-line treatment. Then use the flashcards and the other General Medicine 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.