Abstract 16: IV TPA in the 0-3 Hour Window: Quantitative Fragility-Robustness Assessment of the Strength of the RCT Evidence
Background: After 3 decades, the era of RCTs of IV tPA as a standalone therapy in acute ischemic stroke has now likely closed, with the completion of TESPI, PRISMS, and late, imaging-selection RCTs, and the advent of endovascular thrombectomy. Some non-expert contrarians questioned the accumulating evidence regarding tPA; the recently formulated fragility-robustness index (FRI) enables quantification of the actual rigor of evidence throughout the era of IV tPA investigation. Methods: The FRI summarizing the strength of the statistical evidence for clinical trial findings is the minimum nonevent to event changes needed to turn a statistically significant to non-significant result. The FRI was applied to disability-free (mRS 0-1) and independence (mRS 0-2) outcomes; cumulative meta-analyses delineated evidence strength after each successive RCT. FRI scores were classified: Not Robust (FRI 0-4), Somewhat Robust (5-12), Robust (13-33), and Highly Robust (>33). Results: Systematic search identified 8 RCTs (1960 patients) of IV tPA in the 0-3h window from 1995 - 2018. Study-level meta-analyses showed FRIs of 42 for mRS 0-1 and 40 for mRS 0-2; individual patient data meta-analyses showed FRIs of 40 for both mRS 0-1 and mRS 0-2, placing IV tPA in the highest quintile of FRIs among meta-analyses for all conditions. Evolution of RCT evidence over time is shown in Table 1. Strength of evidence for IV tPA superiority was already robust with publication of the initial 2 NINDS-tPA in 1995, remained robust through 2011 after 4 additional RCTs, increased to highly robust with the IST-3 mega-trial in 2012, and remains highly robust today after 1 additional trial. Conclusions: Intravenous tPA for acute ischemic stroke in 0-3h patients is one of the most robustly proven therapies in medicine. This therapy was already robustly supported with publication of the initial trials 25 years ago and advanced 9 years ago after additional trials to highly robust/non-fragile.