Clinical trials: intention-to-treat analysis: practice question

A PSM 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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PSM · Clinical trials: intention-to-treat analysis

Sample item

In a trial, 200 patients are randomised equally to surgery or medical therapy. In the surgical arm, 30 patients refuse the operation and receive medical therapy instead. To preserve the benefits of randomisation, how should the outcomes be analysed?

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

The answer and the reasoning

D. All 200 patients analysed in the arm to which they were originally randomised

Intention-to-treat analysis keeps every participant in the group to which they were randomised, regardless of what treatment they actually received. This preserves comparable prognostic balance between groups and reflects real-world effectiveness, including non-compliance. Excluding or re-allocating patients (per-protocol or as-treated analysis) reintroduces selection bias.

Option by option

  • A. Only patients who completed their assigned treatment analysed

    A per-protocol analysis includes only completers, who differ systematically from non-completers.

  • B. The 30 non-compliant patients excluded from the analysis

    Excluding the non-compliant patients breaks the comparability of the groups and can bias the result.

  • C. The 30 patients analysed in the medical therapy arm they actually received

    As-treated analysis moves patients on the basis of a post-randomisation behaviour, which is not random.

  • D. All 200 patients analysed in the arm to which they were originally randomised (correct)

    Analysing everyone as randomised maintains the balance created by randomisation.

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.

More PSM questions

Questions about this PSM question

What is the answer to this PSM question?

The best answer is D, All 200 patients analysed in the arm to which they were originally randomised. Intention-to-treat analysis keeps every participant in the group to which they were randomised, regardless of what treatment they actually received.

Why is "Only patients who completed their assigned treatment analysed" not the answer?

A per-protocol analysis includes only completers, who differ systematically from non-completers.

Why is "The 30 non-compliant patients excluded from the analysis" not the answer?

Excluding the non-compliant patients breaks the comparability of the groups and can bias the result.

Why is "The 30 patients analysed in the medical therapy arm they actually rec…" not the answer?

As-treated analysis moves patients on the basis of a post-randomisation behaviour, which is not random.

What concept does this question test?

It tests Clinical trials: intention-to-treat analysis in PSM. This preserves comparable prognostic balance between groups and reflects real-world effectiveness, including non-compliance. Excluding or re-allocating patients (per-protocol or as-treated analysis) reintroduces selection bias.

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 trials: intention-to-treat analysis?

Practise biostatistics with small calculations until sensitivity, predictive values and risk measures are automatic. Then use the flashcards and the other PSM 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.