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Do Patient Characteristics Explain the Differences in Outcome Between Medically Treated Patients in SAMMPRIS and
Seemant Chaturvedi1, Tanya N Turan2, Michael J Lynn2
1From the Department of Neurology, University of Miami, Miami, FL (S.C.); Department of Neurosciences, Medical University of South Carolina, Charleston, SC (T.N.T., M.I.C.); Department of Biostatistics and Bioinformatics, Emory University Rollins School of Public Health, Atlanta, GA (M.J.L.); Mallinckrodt Institute of Radiology and the Departments of Neurology and Neurosurgery, Washington University School of Medicine, St Louis MO (C.P.D.); Department of Neurosurgery, State University of New York, Stony Brook, NY (D.F.); and National Institute of Neurological Disorders and Stroke, National Institute of Health, Bethesda, MD (L.S.J.). SChaturvedi@med.miami.edu.
Insights
Aggressive medical management in the SAMMPRIS trial significantly reduced stroke risk compared to the WASID trial. Adjusting for patient factors confirmed aggressive therapy, not just lower risk, drove better outcomes in preventing recurrent intracranial stenosis stroke.
Area of Science:
- Neurology
- Cardiovascular Research
- Clinical Trials
Background:
- The Stenting and Aggressive Medical Management for Preventing Recurrent Stroke in Intracranial Stenosis (SAMMPRIS) trial showed lower event rates than the Warfarin Aspirin Symptomatic Intracranial Disease (WASID) trial.
- This discrepancy was hypothesized to be due to aggressive medical therapy in SAMMPRIS or lower baseline risk in its patients.
Purpose of the Study:
- To evaluate whether aggressive medical therapy or patient risk factors explain the lower primary endpoint rate in SAMMPRIS compared to WASID.
- To compare the primary endpoint rates between SAMMPRIS and WASID patients with similar qualifying criteria.
Main Methods:
- Proportional hazards regression was used to compare the primary endpoint rates.
- Patients from both SAMMPRIS and WASID trials meeting identical inclusion criteria were analyzed.
- Baseline characteristics were adjusted for confounding factors.
Main Results:
- Unadjusted analysis revealed a significantly higher risk in WASID patients (HR=1.9, P=0.009).
- Key confounding factors identified were lack of statin use (more prevalent in WASID) and prior infarcts (more prevalent in SAMMPRIS).
- After adjusting for these factors, the hazard ratio for WASID versus SAMMPRIS remained significantly higher (HR=1.9, P=0.023).
Conclusions:
- WASID patients faced nearly double the risk of the primary endpoint compared to SAMMPRIS patients after adjusting for baseline characteristics.
- These findings support the hypothesis that aggressive medical management in SAMMPRIS was the primary driver of the reduced event rate.
- The study underscores the importance of comprehensive medical management in preventing recurrent stroke in intracranial stenosis.
Background And Purpose:
The Stenting and Aggressive Medical Management for Preventing Recurrent Stroke in Intracranial Stenosis (SAMMPRIS) medical group had a much lower primary end point rate than predicted from the preceding Warfarin Aspirin Symptomatic Intracranial Disease (WASID) trial. This result has been attributed to the aggressive medical therapy used in SAMMPRIS, but an alternative hypothesis is that SAMMPRIS patients were at lower risk. We undertook analyses to evaluate these competing hypotheses.
Methods:
Using proportional hazards regression, we compared the SAMMPRIS primary end point between SAMMPRIS medical patients and WASID patients meeting the same qualifying criteria adjusted for confounding baseline characteristics.
Results:
The unadjusted comparison of the SAMMPRIS primary end point showed a significantly higher risk for WASID patients (P=0.009, logrank test) with 12 month Kaplan-Meier estimates of 21.9% in WASID and 12.6% in SAMMPRIS and hazard ratio 1.9 (95% confidence interval =1.2-3.0). The analyses identified the following confounding factors that varied between the studies and that conferred a higher risk: lack of statin use at enrollment (hazard ratio =1.8, 95% confidence interval =1.1-2.9, P=0.027) that was more prevalent among WASID patients (39% versus 14%, P<0.0001) and prior infarcts in the territory of the symptomatic vessel (hazard ratio =1.8, 95% confidence interval =1.1-2.9, P=0.023) that was more prevalent among SAMMPRIS patients (34% versus 22%, P=0.015).The hazard ratio for WASID versus SAMMPRIS adjusted for these 2 characteristics was 1.9 (95% confidence interval =1.1-3.2).
Conclusions:
After adjustment for confounding baseline characteristics, WASID patients had an almost 2-fold higher risk of the SAMMPRIS primary end point, which supports the hypothesis that the lower rate of the primary end point in the medical arm of SAMMPRIS compared with WASID patients was as a result of the aggressive medical management used in SAMMPRIS.
Clinical Trial Registration:
URL: http://www.clinicaltrials.gov. Unique identifier: NCT00576693.
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