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Advice on Unblinding

 

 

It should be possible to manage most acute clinical situations by assuming a trial participant has been taking 300mg of aspirin once a day and/or by subsequently withholding the trial medication if appropriate. However, there may be rare clinical circumstances where knowledge of treatment allocation is essential to guide immediate clinical management. Where unblinding is being considered, the case should first be discussed with the MRC CTU or the local trial Principal Investigator wherever possible.

Guidance on a number of anticipated scenarios with specific advice about the need to unblind:

Those who are suspected of having a gastrointestinal bleed should have their trial medication stopped and should be managed according to standard local pathways. Standard treatment for gastrointestinal bleed should be initiated without delay and the patient should be managed by assuming they have been taking aspirin 300mg daily. It is not expected that emergency unblinding will be necessary in the event of acute gastrointestinal bleeding, however if a situation arises where knowledge of the trial treatment allocation would alter the immediate clinical management of a participant, this should be confirmed by the relevant specialist locally and unblinding can be performed.
Those who are suspected of having an intracranial haemorrhage should have their trial medication withheld and should undergo appropriate neuroimaging without delay. If the diagnosis is confirmed then the trial medication should be stopped. It is not expected that emergency unblinding will be necessary in the event of an intracranial haemorrhage, however if a situation arises where knowledge of the trial treatment allocation would alter the immediate clinical management of a participant, this should be confirmed by the relevant specialist locally and unblinding can be performed. Further details of the unblinding process are available here. It should be noted that trial medication can be withheld for up to 3 months while decisions about subsequent management are confirmed. To discuss individual cases with the trial’s vascular advisors please contact the Add-Aspirin team at the MRC CTU during working hours.
The treatment of an ischaemic stroke or TIA often involves the use of aspirin and/or other anti-platelet medication. Standard treatment for an ischaemic stroke or TIA should be initiated without delay, and this may include administration of standard doses of anti-platelet therapy, including aspirin, where indicated. It is possible that a participant may have taken up to a maximum of 300mg of aspirin earlier that day but, under most circumstances, we expect the risks of not treating an ischaemic stroke or TIA to outweigh the potential risks of a higher cumulative dose of aspirin over one day, however clinical judgement should be exercised. It is not expected that emergency unblinding will be necessary in the event of an ischaemic stroke or TIA, however if a clinical situation arises where knowledge of the trial treatment allocation would alter the immediate clinical management of a participant, this should be confirmed by the relevant specialist locally and unblinding can be performed. It should be noted that trial medication can be withheld for up to 3 months while decisions about subsequent management are confirmed. To discuss individual cases with the trial’s vascular advisors please contact the Add-Aspirin team at the MRC CTU during working hours.
If a situation arises where an overdose of trial medication is suspected (either by the participant, or another individual), advice on the management of a suspected aspirin overdose is available from the National Poisons Information Service at www.toxbase.org. Standard management includes blood salicylate levels, which may reveal trial treatment allocation. Where doubt exists the patient should be managed assuming they have taken 300mg aspirin tablets. If a situation arises where knowledge of the trial treatment allocation would alter the immediate clinical management of the individual involved, unblinding can be performed. Further details of the unblinding process are available here.
When a surgical intervention is planned, anti-platelet therapy is often withheld temporarily. Trial treatment can be withheld for up to 3 months but please ensure that the MRC CTU is informed. .
For participants who require emergency surgery, where knowledge of treatment allocation would alter immediate surgical management, this should be confirmed by the surgeon involved locally and unblinding can be performed. Further details of the unblinding process are available here.

Contact Details

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