The external validity—in other words, the transferability to real-world clinical practice—of contemporary randomised controlled trials (RCTs) investigating carotid artery stenosis interventions “varies considerably”, as per a recent analysis published in the European Journal of Vascular and Endovascular Surgery (EJVES) by senior author Hans-Henning Eckstein, first author Michael Kallmayer (both Technical University of Munich, Munich, Germany) and colleagues.
For this study, researchers aimed to analyse the exclusion criteria of recent RCTs comparing the two leading carotid revascularisation approaches—carotid endarterectomy (CEA) and carotid artery stenting (CAS)—with the intention of assessing the eligibility of consecutive clinical practice cohorts compared to those RCTs.
An analysis of the clinical and anatomical exclusion criteria of RCTs for asymptomatic carotid artery stenosis (SPACE-2, ACST-2, CREST-1 and CREST-2) and symptomatic carotid artery stenosis (SPACE-1, CREST-1, ICSS and EVA-3S) was performed, the authors report.
A total of 200 consecutive asymptomatic and 200 consecutive symptomatic patients, treated by CEA or transfemoral/transcarotid artery stenting at a tertiary referral university centre, were assessed for their potential eligibility for each corresponding RCT. Patient data from the selected trials were pooled and differences from the clinical practice cohort analysed. The authors note that statistics were descriptive and comparative using Fisher’s exact and t tests.
“The number of clinical and anatomical exclusion criteria differed widely between RCTs,” Eckstein, Kallmayer and colleagues write, relaying their results in EJVES.
Potential eligibility rates of the clinical practice cohort for RCTs with regard to asymptomatic carotid stenosis were 80.5% (ACST-2), 79.5% (SPACE-2), 47% (CREST-1) and 20% (CREST-2). For RCTs on symptomatic carotid stenosis, the eligibility rates were found to be 89% (ICSS), 86.5% (EVA-3S), 64% (SPACE-1) and 39% (CREST-1).
Both clinical practice cohorts were older by about three years, and patients were more often male, when compared to the carotid RCT populations, the authors also report.
“Furthermore, a history of smoking (asymptomatic patients), hypertension (symptomatic patients), and atrial fibrillation was diagnosed more often [in the clinical practice cohorts], whereas hypercholesterolaemia and coronary heart disease (asymptomatic patients) were less prevalent,” Eckstein, Kallmayer and colleagues continue. “More clinical practice patients were on antiplatelets, anticoagulants and lipid-lowering drugs. Symptomatic clinical practice patients presented more often with retinal ischaemia and less often with minor hemispheric strokes than patients in the RCTs.”
The authors conclude that, as such, patients in routine clinical practice differ from the selected carotid intervention trial populations with respect to age, comorbidities and medication.
“These data are of interest for clinicians and guideline authors, and may be relevant for the design of future comparative trials,” they add.