General pharmacology and pharmacokinetics: Cockcroft-Gault estimation: practice question

A Pharmacology 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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Pharmacology · General pharmacology and pharmacokinetics: Cockcroft-Gault estimation

Sample item

Before prescribing gentamicin to a 70-year-old woman, a resident estimates her creatinine clearance using the Cockcroft-Gault equation. Which set of variables does the equation use?

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

The answer and the reasoning

A. Age, body weight, serum creatinine and sex

Cockcroft-Gault estimates creatinine clearance from age, body weight, serum creatinine and sex (with a correction factor for women). It is widely used to adjust doses of renally cleared drugs. MDRD-type equations estimate GFR and do not use body weight.

Option by option

  • A. Age, body weight, serum creatinine and sex (correct)

    Correct. Age, weight, serum creatinine and sex are the inputs of Cockcroft-Gault.

  • B. Body surface area, urine creatinine and urine volume

    Urine creatinine and urine volume are used in a measured timed urine collection, not in this estimate.

  • C. Age, serum creatinine, sex and race, without body weight

    This describes an MDRD-type eGFR equation, which does not use body weight.

  • D. Serum cystatin C, age and sex

    Cystatin C equations are separate eGFR methods and not part of Cockcroft-Gault.

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 Pharmacology question

What is the answer to this Pharmacology question?

The best answer is A, Age, body weight, serum creatinine and sex. Cockcroft-Gault estimates creatinine clearance from age, body weight, serum creatinine and sex (with a correction factor for women).

Why is "Body surface area, urine creatinine and urine volume" not the answer?

Urine creatinine and urine volume are used in a measured timed urine collection, not in this estimate.

Why is "Age, serum creatinine, sex and race, without body weight" not the answer?

This describes an MDRD-type eGFR equation, which does not use body weight.

Why is "Serum cystatin C, age and sex" not the answer?

Cystatin C equations are separate eGFR methods and not part of Cockcroft-Gault.

What concept does this question test?

It tests General pharmacology and pharmacokinetics: Cockcroft-Gault estimation in Pharmacology. It is widely used to adjust doses of renally cleared drugs. MDRD-type equations estimate GFR and do not use body weight.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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 General pharmacology and pharmacokinetics: Cockcroft-Gault estimation?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology 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.