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Reanalysis of stroke data confirms benefit of TPA.

KISSIMMEE, FLA. -- A reanalysis of data from a pivotal stroke trial confirms a robust beneficial treatment effect of intravenous tissue plasminogen activator, Dr. Jeffrey L. Saver reported at the 31st International Stroke Conference.

The National Institute of Neurological Disorders and Stroke Tissue Plasminogen Activator (NINDS-TPA) stroke trials I and II, which were published a decade ago, showed a significant benefit with TPA treatment, but the differences in stroke severity at presentation among the treatment and placebo groups led some critics, including those in the emergency medicine community, to question the results of these trials, said Dr. Saver of the University of California, Los Angeles.

Several reanalyses using traditional methods have been performed, but some critics have remained unconvinced.

The new reanalysis offers additional evidence of the value of TPA. "I don't know if this is going to be enough to convince the confirmed skeptics of the trials, but I believe for the rest of us it provides reassurance that the pivotal trials supporting TPA under 3 hours were indeed positive," Dr. Saver said.

Using a novel and emerging baseline severity-adjusted end-point reanalysis known as responder analysis or sliding dichotomy analysis, Dr. Saver adjusted for the baseline differences and found that in both NINDS-TPA I and II, patients treated with TPA were significantly more likely than were placebo patients to experience good outcomes.

Pooled data from the 624 patients in the two trials showed that 38% of TPA patients, compared with 26% of placebo patients, experienced good outcomes (odds ratio 1.68), Dr. Saver said at the conference, which was sponsored by the American Stroke Association.

Because a greater proportion of patients with mild stroke were known to have presented within 90 minutes than within 91-180 minutes following the event, Dr. Saver also analyzed these groups separately using combined data from the two trials.

Among those presenting from 0 to 90 minutes, good outcomes with TPA vs. placebo patients occurred in 39% vs. 29% of patients, respectively (odds ratio 1.56--showing a strong trend favoring TPA), he reported.

Among the patients presenting from 91 to 180 minutes--the group of most concern due to greater baseline differences in stroke severity--good outcomes with TPA vs. placebo were seen in 36% vs. 24% of TPA and placebo patients, respectively (odds ratio of 1.8., showing a statistically significant benefit of TPA).

After adjustment for 15 covariates that were identified in the literature as predictors of acute stroke outcome, the odds ratios favoring TPA further increased, Dr. Saver noted.

For example, In the NINDS-TPA II trial, the odds ratio changed from 1.74 to 2.2 in favor of TPA, he said.

With this novel approach to data analysis, as used in the more recent Abciximab in Emergent Stroke Treatment and Glycine Antagonist in Neuroprotection trials, good outcomes are defined as a 3-month modified Rankin Score of 0 in those with a pretreatment National Institutes of Health Stroke Scale (NIHSS) score of 0-7, a modified Rankin Score of 0-1 in those with a pretreatment NIHSS score of 8-14, or a modified Rankin Score of 0-2 in those with a pretreatment NIHSS score of greater than 14.

'Adding to the several analyses in the literature that attempt to use traditional means to take into account baseline imbalances in (the NINDS-TPA trials), this entirely complementary and novel approach of sliding dichotomy also shows robust treatment effects," Dr. Saver said.

The reanalysis further shows that the benefits extend through the full 3-hour treatment window, he noted.


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Title Annotation:News; tissue plasminogen activator
Author:Worcester, Sharon
Publication:Internal Medicine News
Geographic Code:1USA
Date:Aug 1, 2006
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