Late-window mechanical thrombectomy appears to lead to “at least the same likelihood” of favourable clinical outcomes in unwitnessed versus witnessed large vessel occlusion (LVO) stroke patients, as per a secondary analysis of the CLEAR study published recently in the journal Stroke.
In analyses including more than 2,000 patients treated at sites across Europe, North America and Asia, functional independence was achieved by 38.8% of unwitnessed and 45.7% of witnessed patients (p=0.022). Mortality and haemorrhage rates were comparable and, after weighting, the primary outcome of modified Rankin scale (mRS) shift showed no significant difference between groups (odds ratio [OR], 1.35; p=0.235). However, while several other secondary outcomes were also similar, unwitnessed patients demonstrated slightly higher odds of functional independence or return of mRS to pre-stroke levels (OR, 1.53; p=0.045).
“Our results show that functional and safety outcomes for witnessed and unwitnessed patients are very similar in the extended time window,” said Liisa Tomppo (University of Helsinki, Helsinki, Finland), the study’s corresponding author, speaking with NeuroNews. “A patient’s witness status should not guide treatment decisions, and no patient should be denied endovascular treatment based on their witness status if otherwise eligible.”
Relaying their findings in Stroke, Tomppo and colleagues say they enrolled adults with anterior-circulation LVO strokes undergoing a thrombectomy 6–24 hours from time last seen well within the CLEAR study—a multicentre investigation originally devised to compare outcomes between different diagnostic approaches for late-window case selection.
The researchers included a total of 2,073 patients, of whom the majority had unwitnessed (84.9%) versus witnessed (15.1%) stroke onsets. Unwitnessed patients were those whose stroke was not witnessed by an observer, leading to their time last seen well being used as their symptom onset time, while witnessed patients’ stroke onset was reported to have been seen by an observer or reported by the patient themself.
Comparisons of the unwitnessed versus witnessed patients using inverse probability of treatment weighting (IPTW) regression analyses affirmed that the primary outcome, 90-day mRS ordinal shift, was statistically similar across groups. And, while IPTW regression indicated that unwitnessed patients were more likely to achieve functional independence or a return to baseline mRS at 90 days than witnessed patients, there were no significant differences in functional independence alone nor in safety outcomes including symptomatic intracranial haemorrhage (sICH), mortality, or a composite of 90-day severe disability or mortality.
Furthermore, according to the researchers, interaction analyses “suggested that males and transferred patients had a higher likelihood of favourable outcomes if their onset of symptoms was unwitnessed”. However, no interaction was observed for functional independence nor return to baseline mRS within these subgroups.
“Although neither sex showed a significant difference between unwitnessed and witnessed onset on the primary outcome, males were slightly more likely to benefit from unwitnessed status,” Tomppo et al state. “One possible explanation for the sex difference is that females are more often unwitnessed because they live alone and are unable to seek treatment themselves. Previous studies have shown that transferred patients experience longer treatment delays but a similar likelihood of good functional outcomes. In our cohort, patients who were transferred were more likely to benefit from being unwitnessed. Further studies should investigate how transfer status affects outcomes in various patient subgroups.”
