Intention-to-Treat vs Per-Protocol: What the Comparison Means
Intention-to-treat and per-protocol approaches concern different questions about an intervention. Read the analysis methods before using either result in a nursing evidence summary.
The worked examples are teaching aids. Check them against your own source material and the requirements of your specific task.
Start with the task
Cochrane's trial-bias chapter distinguishes the effect of assignment from the effect of adhering to a protocol.
Identify the question behind the estimate
In a fictional trial of an educational programme, some assigned participants attend every session and others do not. An intention-to-treat analysis aims to preserve the original group allocation. A per-protocol effect concerns adherence to the specified intervention.
Simply analysing attenders is not automatically an unbiased estimate of adherence. Attenders may differ from non-attenders in ways related to the outcome.
Read beyond the label
Check which participants were included, which groups they were analysed in, what outcomes were missing, and how missing data were handled. Papers do not always use analysis labels consistently.
Make a small note with three rows: assigned population, analysed population, and reason for any difference. Do not assume that “intention-to-treat” means every outcome was observed.
If a paper reports several analyses, avoid selecting the most favourable result without explaining why it answers your question.
Match the claim to the analysis
A rationale about offering a programme differs from a claim about what happens when people fully follow it. Neither directly predicts what will happen for an individual in a supplied case.
Write the comparison accurately and retain any important selection or missing-data limitation. If the methods are unclear, mark that uncertainty rather than giving the estimate a stronger interpretation.
The rationale guide helps place the claim in context. Nursevi can organise the source and qualification, while appraisal and appropriate professional guidance determine how it informs the assignment.