There is limited experience in using deferred consent for studies involving children, which was legalized in the United Kingdom in 2008. We aimed to inform future studies by evaluating consent rates and reasons for nonconsent in a large randomized controlled trial in pediatric intensive care.


In the CATCH trial, eligible children from 14 PICUs in England and Wales were randomly assigned to 3 types of central venous catheters. To avoid delay in treatment, children admitted on an emergency basis were first randomly assigned to a trial central venous catheter, and we deferred seeking consent to use already collected data and blood samples until after stabilization.


Consent was obtained for 984/1358 (72%) of children admitted on an emergency basis. Failure to obtain consent resulted mainly from a lack of opportunity (early discharge or transfer) for survivors and difficulties in seeking consent for children who died. For admissions where there was an opportunity to approach (n = 1298), inclusion rates differed according to survival status: 93/984 (9%) of consented patients died, compared with 58/314 (18%) of nonconsented patients. For children admitted on an emergency basis whose families were approached, 984/1178 (84%) provided deferred consent (n = 15 sites), compared with 441/641 (69%) of children admitted on an elective basis who were approached for prospective consent (n = 9 sites).


Design of emergency randomized controlled trials should balance the potential burden that seeking consent in difficult situations may cause against risk of bias by disproportionately excluding children who die or are transferred. Ethics committees could consider approving the use of already collected data when best efforts to obtain deferred consent are unsuccessful.

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