Factors influencing the use of different methods of consent in a randomized acute stroke trial: The Third International Stroke Trial (IST-3)

BACKGROUND: Obtaining informed consent in people with acute stroke is complex since many, as a direct result of their stroke, lose capacity to make important decisions. Furthermore, reperfusion interventions are time dependent necessitating rapid consent. We developed four different consent approaches to facilitate recruitment of a broad range of patients in the Third International Stroke Trial (IST-3). AIMS: To describe the clinical characteristics of patients recruited by different consent methods and the association between these methods and time from stroke onset to randomization. METHODS: IST-3 was a randomized controlled trial of thrombolysis for acute ischemic stroke. Clinicians could use one of four consent procedures: written consent, witnessed consent, assent, or a waiver of consent. We analyzed the relationship between consent procedure and baseline variables. The effect of consent procedure on delay time from onset to randomization was determined using analysis of variance to adjust for confounding effects. RESULTS: Of the 3035 patients recruited, the method of consent was known for 3034 (99.9%), and it was written in 985 subjects (32.5%), witnessed verbal consent in 280 (9.2%), assent by relative in 1727 (56.9%), and waiver of consent in 42 subjects (1.4%). Assent was required in 63.4% for those presenting 0–3 h from stroke onset (written consent in 25.3%). Patients with more severe neurological deficits (or with a non-lacunar hemispheric stroke syndrome) were less likely to give written consent. Mean delay between onset and randomization varied significantly between consent types (one-way analysis of variance: F = 15.7 on 3 df, p < 0.0001) (longest at 4.06 h for signed consent and 3.46 h for waiver of consent). CONCLUSIONS: Acute stroke trials requiring written informed consent would result in substantial selection bias. Flexible consent methods will ensure a broad range of patients are recruited, enabling trial results to be widely generalizable. Registration: This study’s registered number is ISRCTN25765518.