Eight RCTs were included in the review (11,360 patients) comprising six trials of asymptomatic patients (5,733 patients) and two trials of symptomatic patients (5,627 patients). Mean follow-up duration ranged from 23.6 months to five years (where reported). All trials had high risk of bias for blinding of patients and personnel. Six trials had a high risk for other bias. Four trials had low risk of bias for all other quality domains assessed; four had low risk of bias for all but one of the other quality domains.
Asymptomatic patients: No significant difference was found for risk of stroke or death between two and four years follow-up among groups that received carotid endarterectomy plus medical therapy versus those that received medical therapy alone (RR 0.93, 95% CI 0.84 to 1.02; six trials; Ι²=0%). A small but significantly higher risk of death was shown among carotid endarterectomy plus medical therapy groups versus medical therapy alone groups (RR 1.14, 95% CI 1.03 to 1.25). No statistically significant relationship was found between the year of publication and the effect size (p=0.81).
Symptomatic patients: For patients with severe stenosis (50% or more using the NASCET technique, or 70% or more using the ECST technique), there was a statistically significant lower risk of stroke or death among groups that received carotid endarterectomy plus medical therapy compared with the group that received medical therapy alone from two to five years follow-up (RR 0.69, 95% CI 0.59 to 0.81, two trials, Ι²=17%). The number needed to treat was 11 patients (95% CI 8 to 17). For patients with stenosis that was not severe, no statistically significant differences in the risk of stroke or death were reported between the two groups (reported fully in paper).