Do Postmarketing Surveillance Studies Represent Real-World Populations? A Comparison of Patient Characteristics and Outcomes After Carotid Artery Stenting

Study Questions:

Do postmarketing surveillance (PMS) studies accurately reflect the outcomes of unselected patients undergoing carotid artery stenting?


The authors used the National Cardiovascular Database Registry–Carotid Artery Revascularization and Endarterectomy (NCDR CARE) Registry to compare the baseline characteristics and in-hospital outcomes of patients undergoing carotid stenting who were enrolled in a PMS study with those who were not enrolled in such studies. Propensity adjustment was used to adjust for multiple confounding differences.


Patients participating in PMS studies were less likely to have symptomatic disease (31.5% vs. 58.2%; p < 0.001) or acute evolving stroke (1.0% vs. 3.9%; p < 0.001), and more likely to undergo stenting using emboli protection devices (94.5% vs. 88.9%). Patients in the PMS studies had a lower rate of in-hospital stroke (1.7% vs. 2.7%; p = 0.005) or death (0.3% vs. 1.4%; p < 0.001). Enrollment in the PMS studies was associated with a lower risk of early (odds ratio, 0.44; 95% confidence interval, 0.21-0.95; p = 0.04) and 2-year death (hazard ratio, 0.80; 95% confidence interval, 0.66-0.97; p = 0.02) in a propensity-adjusted analysis.


The authors concluded that patients enrolled in PMS studies of carotid stenting represent a less sick cohort, and have lower mortality compared with patients who are not enrolled in such studies.


This study elegantly demonstrates the limitations of using solely PMS studies to track outcomes of carotid stenting (and by extension, other new procedures). The patients who agree to participate in research are generally healthier and have better outcomes than those who do not participate in research. This self selection, combined with the lower neurological risk of the patients in the PMS studies, likely explains the better outcome seen in this cohort. It would be preferable if the Food and Drug Administration would mandate studies/registries to track all consecutive patients as new products or new procedures are approved so that the outcome of the procedure in the real world could be determined with greater accuracy.

Clinical Topics: Invasive Cardiovascular Angiography and Intervention

Keywords: Endarterectomy, Registries, Embolic Protection Devices, Carotid Arteries, United States, Stents

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