The principle of an ‘intention to treat’ analysis is that the participants in a randomised\u00a0trial are analysed in the group to which they were randomised, regardless of what treatment they received. So in a hypothetical trial of salbutamol vs. aminophiline\u00a0infusion for severe asthma, regardless of what the child got, they are placed in their ‘you should have’ group…<\/p>\n
The concept\u00a0comes from the core of RCT philosophy – that chance has settled all prognostic factors evenly between the two* arms – and so the only reasonable way of preserving this is to analyse the outcomes according to this\u00a0sorting.<\/p>\n
What this does is, if some folk in the ‘intervention’ arm don’t get the intervention (e.g.\u00a0Salbutamol infusion, but their K+ was falling prior to starting) then it reduces the observed effect of the drug. This is then ‘unfair’.<\/p>\n
But wait. Pragmatic RCTs, ones of treatments as we use them, test an intervention. They test not ‘salbutamol infusion’ but the intervention – which might be characterised as ‘what if we have an approach that says we should use salbutamol infusions for pts unless its clear they need something different … like PICU .. now … can someone ring 2222 please …’<\/p>\n
If there are lots of deviations, crossovers and non-receipts of the allocated intervention, it’s very important to looks why. The way we were proposing to do ‘the intervention’ clearly doesn’t work in practice — so it needs reassessing — not necessarily having the ‘treatment’ element thrown out.<\/p>\n
– Archi<\/p>\n
* OK – so it could be three, four etc arms. It’s just that two is easier to think about. And commonerer.<\/p>\n","protected":false},"excerpt":{"rendered":"
The principle of an ‘intention to treat’ analysis is that the participants in a randomised\u00a0trial are analysed in the group to which they were randomised, regardless of what treatment they received. So in a hypothetical trial of salbutamol vs. aminophiline\u00a0infusion for severe asthma, regardless of what the child got, they are placed in their ‘you […]<\/p>\n