Prediction modelling the impact of onset to treatment time on the modified Rankin Scale score at 90 days for patients with acute ischaemic stroke.

Shortening the time from stroke onset to treatment increases the effectiveness of endovascular stroke therapies. This study aimed to predict the modified Rankin Scale score at 90 days post-stroke (mRS-90d score) in patients with acute ischaemic stroke (AIS) with respect to four types of treatment: conservative therapy (CVT), intravenous thrombolysis only (IVT), mechanical thrombectomy only (MT) and pretreatment with IVT before MT (IVT+MT). This nationwide observational study included 124 484 confirmed cases of acute stroke in Sweden over 6 years (2012-2017). The associations between onset-to-treatment time (OTT), patient age and hospital admission National Institutes of Health Stroke Scale (NIHSS) score with the five-levelled mRS-90d score were retrospectively studied. A generalised linear model (GLM) was fitted to predict the mRS-90d scores for each patient group. The fitted GLM for CVT patients is a function of age and NIHSS score. For IVT, MT and IVT+MT patients, GLMs additionally employed OTT variables. By reducing the mean OTTs by 15 min, the number needed-to-treat (NNT) for one patient to make a favourable one-step shift in the mRS was 30 for IVT, 48 for MT and 21 for IVT+MT. This study demonstrates linear associations of mRS-90d score with OTT for IVT, MT and IVT+MT, and shows in absolute effects measures that OTT reductions for IVT and/or MT produces substantial health gains for patients with AIS. Even moderate OTT reductions led to sharp drops in the NNT.

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Competing interests: NEV reports academic grants from Linköping University, and has had research contract with Bayer. TT reports academic grants from University of Gothenburg, Sahlgrenska University Hospital, Sigrid Juselius Foundation and Wennerström Foundation. He has/has had research contracts with Bayer, Boehringer Ingelheim, Bristol Myers Squibb and Portola Pharm. He has/has had advisory board memberships with Bayer, Boehringer Ingelheim, Bristol Myers Squibb and Portola Pharm. TT has filed two international patents: new therapeutic uses (method to prevent brain oedema and reperfusion injury), and thrombolytic compositions (method to prevent post-thrombolytic haemorrhage formation). PW reports academic grants from University of Umeå and the Swedish Heart and Lung foundation. He has/has had research contracts with Abbott and Bristol Myers Squibb. JL reports no conflict of interest. L-ÅL has/has had research contracts with Bayer, Boehringer Ingelheim, AstraZeneca and Janssen. He has/has had attained advisory boards with Bayer, Boehringer Ingelheim, Pfizer, BMS, MSD and GSK.