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Sat Jul 31 17:10:40 BST 2010

On 30 July 2010 13:53, Robert Smith <rfsmithmd at comcast.net> wrote:

> The results of the CRASH 2 study were recently published in the Lancet.
>
> [...]
>
> I had two questions. Regarding enrollment:
>
> "Adult trauma patients with significant haemorrhage (systolic blood
> pressure <90 mm Hg or heart rate >110 beats per min, or both), or who were
> considered to be at risk of significant haemorrhage, and who were within 8 h
> of injury, were eligible for the trial. Patients were included if the
> responsible doctor was substantially uncertain about whether or not to treat
> with tranexamic acid (ie, entry was governed by the uncertainty principle).8
> Patients for whom the responsible doctor considered that there was a clear
> indication for tranexamic acid were not randomly assigned. Similarly,
> patients for whom there was considered to be a clear contraindication to
> tranexamic acid treatment were not randomly assigned. However, when the
> responsible doctor was substantially uncertain as to whether or not to treat
> with this agent, these patients were eligible for randomisation."
>
> This seemed an unusual criteria. Was this done because of ethical reasons?
> Would this type of enrollment tend to lessen the observed treatment effect?
> That is, if patients who were clearly thought to benefit from the drug were
> included, would a greater effect have been seen?
>

Yes.  Basically there had to be equipoise for the enrolling clinician
regarding the utility of tranexamic acid in the patient.  If the doctor
firmly believed that the patient should have TXA (or not) then they were not
randomised.  This is just good practice for a clinical study although there
clearly may then be bias introduced - although this would be more important
if the drug was found to be ineffective (ie patients who needed it got it
because doctor's believed and the study only randomised patients who would
not benefit)

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