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Archimedes
Towards evidence based medicine for paediatricians Edited by Bob Phillips Intention to treat The principle of an ‘intention to treat’ analysis is that the participants in a randomised trial are analysed in the group to which they were randomised, regardless of what treatment they received. So, in a hypothetical trial of salbutamol versus aminophylline infusion for severe asthma, regardless of what the child has got, they are placed in their ‘you should have’ group… The concept comes from the core of the philosophy of randomised controlled trials (RCT)—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 sorting. The effect of this, if some folk in the ‘intervention’ arm do not get the intervention (eg, salbutamol infusion, but their K+ was falling prior to starting, and so they never got it, or in the aminophylline group, the child was vomiting, and it just seemed unreasonable to make it worse) then it reduces the observed effect of the drug. Surely, this is then ‘unfair’? But wait. Pragmatic RCTs, ones of treatments as we use them, test an intervention approach. They do not test ‘salbutamol infusion’ or ‘aminophylline infusion’, but the approach to intervention, which might be characterised as ‘which is better, using salbutamol infusions or aminophylline infusions for pts unless for some reason it’s clear they need something different… like PICU… now… actually… can someone ring 2222 please?’ If there are lots of deviations, crossovers and non-receipts of the allocated intervention, it is very important to look closely why. The way we were proposing to do ‘the intervention’ clearly does not work in practice—so it needs reassessing—not necessarily concluding that ‘the treatment’ element does not work, and is thrown out. Bob Phillips Correspondence to Dr Bob Phillips, Centre for Reviews and Dissemination, University of York, York YO10 5DD, UK; [email protected] Competing interests None declared. Provenance and peer review Commissioned; internally peer reviewed. Received 18 June 2015 Accepted 19 June 2015
Arch Dis Child 2015;100:803. doi:10.1136/archdischild-2015-309200
Arch Dis Child August 2015 Vol 100 No 8
803
Downloaded from http://adc.bmj.com/ on November 18, 2015 - Published by group.bmj.com
Towards evidence based medicine for paediatricians Arch Dis Child 2015 100: 803
doi: 10.1136/archdischild-2015-309200 Updated information and services can be found at: http://adc.bmj.com/content/100/8/803.2
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Articles on similar topics can be found in the following collections ADC Archimedes (227) Drugs: respiratory system (108) Child health (3818) Asthma (363) Competing interests (ethics) (174) Immunology (including allergy) (1957) Journalology (227)
Notes
To request permissions go to: http://group.bmj.com/group/rights-licensing/permissions To order reprints go to: http://journals.bmj.com/cgi/reprintform To subscribe to BMJ go to: http://group.bmj.com/subscribe/
Archimedes
Towards evidence based medicine for paediatricians Edited by Bob Phillips Intention to treat The principle of an ‘intention to treat’ analysis is that the participants in a randomised trial are analysed in the group to which they were randomised, regardless of what treatment they received. So, in a hypothetical trial of salbutamol versus aminophylline infusion for severe asthma, regardless of what the child has got, they are placed in their ‘you should have’ group… The concept comes from the core of the philosophy of randomised controlled trials (RCT)—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 sorting. The effect of this, if some folk in the ‘intervention’ arm do not get the intervention (eg, salbutamol infusion, but their K+ was falling prior to starting, and so they never got it, or in the aminophylline group, the child was vomiting, and it just seemed unreasonable to make it worse) then it reduces the observed effect of the drug. Surely, this is then ‘unfair’? But wait. Pragmatic RCTs, ones of treatments as we use them, test an intervention approach. They do not test ‘salbutamol infusion’ or ‘aminophylline infusion’, but the approach to intervention, which might be characterised as ‘which is better, using salbutamol infusions or aminophylline infusions for pts unless for some reason it’s clear they need something different… like PICU… now… actually… can someone ring 2222 please?’ If there are lots of deviations, crossovers and non-receipts of the allocated intervention, it is very important to look closely why. The way we were proposing to do ‘the intervention’ clearly does not work in practice—so it needs reassessing—not necessarily concluding that ‘the treatment’ element does not work, and is thrown out. Bob Phillips Correspondence to Dr Bob Phillips, Centre for Reviews and Dissemination, University of York, York YO10 5DD, UK; [email protected] Competing interests None declared. Provenance and peer review Commissioned; internally peer reviewed. Received 18 June 2015 Accepted 19 June 2015
Arch Dis Child 2015;100:803. doi:10.1136/archdischild-2015-309200
Arch Dis Child August 2015 Vol 100 No 8
803
Downloaded from http://adc.bmj.com/ on November 18, 2015 - Published by group.bmj.com
Towards evidence based medicine for paediatricians Arch Dis Child 2015 100: 803
doi: 10.1136/archdischild-2015-309200 Updated information and services can be found at: http://adc.bmj.com/content/100/8/803.2
These include:
Email alerting service
Topic Collections
Receive free email alerts when new articles cite this article. Sign up in the box at the top right corner of the online article.
Articles on similar topics can be found in the following collections ADC Archimedes (227) Drugs: respiratory system (108) Child health (3818) Asthma (363) Competing interests (ethics) (174) Immunology (including allergy) (1957) Journalology (227)
Notes
To request permissions go to: http://group.bmj.com/group/rights-licensing/permissions To order reprints go to: http://journals.bmj.com/cgi/reprintform To subscribe to BMJ go to: http://group.bmj.com/subscribe/
