Stroke aetiological classification reliability and effect on trial sample size : systematic review, meta-analysis and statistical modelling

BackgroundInter-observer variability in stroke aetiological classification may have an effect on trial power and estimation of treatment effect. We modelled the effect of misclassification on required sample size in a hypothetical cardioembolic (CE) stroke trial.MethodsWe performed a systematic review to quantify the reliability (inter-observer variability) of various stroke aetiological classification systems. We then modelled the effect of this misclassification in a hypothetical trial of anticoagulant in CE stroke contaminated by patients with non-cardioembolic (non-CE) stroke aetiology. Rates of misclassification were based on the summary reliability estimates from our systematic review. We randomly sampled data from previous acute trials in CE and non-CE participants, using the Virtual International Stroke Trials Archive. We used bootstrapping to model the effect of varying misclassification rates on sample size required to detect a between-group treatment effect across 5000 permutations. We described outcomes in terms of survival and stroke recurrence censored at 90days.ResultsFrom 4655 titles, we found 14 articles describing three stroke classification systems. The inter-observer reliability of the classification systems varied from fair' to very good' and suggested misclassification rates of 5% and 20% for our modelling. The hypothetical trial, with 80% power and alpha 0.05, was able to show a difference in survival between anticoagulant and antiplatelet in CE with a sample size of 198 in both trial arms. Contamination of both arms with 5% misclassified participants inflated the required sample size to 237 and with 20% misclassification inflated the required sample size to 352, for equivalent trial power. For an outcome of stroke recurrence using the same data, base-case estimated sample size for 80% power and alpha 0.05 was n=502 in each arm, increasing to 605 at 5% contamination and 973 at 20% contamination.ConclusionsStroke aetiological classification systems suffer from inter-observer variability, and the resulting misclassification may limit trial power.Trial registrationProtocol available at reviewregistry540.Peer reviewe

Stroke aetiological classification reliability and effect on trial sample size: systematic review, meta-analysis and statistical modelling

Background: Inter-observer variability in stroke aetiological classification may have an effect on trial power and estimation of treatment effect. We modelled the effect of misclassification on required sample size in a hypothetical cardioembolic (CE) stroke trial. Methods: We performed a systematic review to quantify the reliability (inter-observer variability) of various stroke aetiological classification systems. We then modelled the effect of this misclassification in a hypothetical trial of anticoagulant in CE stroke contaminated by patients with non-cardioembolic (non-CE) stroke aetiology. Rates of misclassification were based on the summary reliability estimates from our systematic review. We randomly sampled data from previous acute trials in CE and non-CE participants, using the Virtual International Stroke Trials Archive. We used bootstrapping to model the effect of varying misclassification rates on sample size required to detect a between-group treatment effect across 5000 permutations. We described outcomes in terms of survival and stroke recurrence censored at 90 days. Results: From 4655 titles, we found 14 articles describing three stroke classification systems. The inter-observer reliability of the classification systems varied from ‘fair’ to ‘very good’ and suggested misclassification rates of 5% and 20% for our modelling. The hypothetical trial, with 80% power and alpha 0.05, was able to show a difference in survival between anticoagulant and antiplatelet in CE with a sample size of 198 in both trial arms. Contamination of both arms with 5% misclassified participants inflated the required sample size to 237 and with 20% misclassification inflated the required sample size to 352, for equivalent trial power. For an outcome of stroke recurrence using the same data, base-case estimated sample size for 80% power and alpha 0.05 was n = 502 in each arm, increasing to 605 at 5% contamination and 973 at 20% contamination. Conclusions: Stroke aetiological classification systems suffer from inter-observer variability, and the resulting misclassification may limit trial power. Trial registration: Protocol available at reviewregistry540

Shock Index Predicts up to 90-day Mortality Risk after Intracerebral Haemorrhage

ACKNOWLEDGEMENTS The following individuals should be indexed on PubMed as collaborators - VISTA-ICH Steering Committee: DF Hanley (Chair), K Butcher, S Davis, B Gregson, KR Lees, P Lyden, S Mayer, K Muir, and T SteinerPeer reviewedPostprin

Antiplatelet therapy following ischaemic stroke: continue or change pre-existing therapy?

Introduction: Antiplatelet therapy is routinely prescribed early after ischaemic stroke. Many patients will already be taking antiplatelet therapy and it is unknown whether these patients should continue the same antiplatelet treatment or switch to a different regimen. Methods:We selected patients with ischaemic stroke from the Virtual International Stroke Trials Archive database who were prescribed antiplatelets both before and after their stroke and who had detailed records of adverse events after stroke. We compared patients who changed to a new antiplatelet regimen after their stroke to those who continued the same regimen. The primary outcome was recurrent ischaemic stroke within 90 days after their index stroke and the secondary outcome was intracranial haemorrhage (ICH) or extracranial haemorrhage (ECH). We used logistic regression analysis and adjusted for age and baseline NIHSS. Results: A total of 1129 participants were included. Of these, 538 subjects changed antiplatelet regimen post stroke and 591 continued the same regimen. A recurrent ischaemic event occurred in 4.1% of subjects who changed regimen and 4.3% who continued unchanged (adjusted OR¼0.93; 95% CI 0.54–1.75, p¼0.929). The incidence of ICH and ECH within the first 90 days was similar in both groups (2.4% vs. 2.6% (adjusted OR¼1.02; 95% CI 0.48–2.18, p¼0.955) and 4.7% vs. 2.9% (adjusted OR¼1.82; 95% CI 0.96–3.43, p¼0.065), respectively). Discussion: The analysis was performed using a non-randomised registry data. Conclusion: In patients who suffer ischaemic stroke whilst taking antiplatelets, a change in antiplatelet regimen was not associated with an altered risk of early recurrent ischaemic stroke rate or bleeding. However, the results must be interpreted in view of the low event rates

The smoking paradox in ischemic stroke patients treated with intra-arterial thrombolysis in combination with mechanical thrombectomy-VISTA-Endovascular

Background The smoking-paradox of a better outcome in ischemic stroke patients who smoke may be due to increased efficacy of thrombolysis. We investigated the effect of smoking on outcome following endovascular therapy (EVT) with mechanical thrombectomy alone versus in combination with intra-arterial (IA-) thrombolysis.Methods The primary endpoint was defined by three-month modified Rankin Scale (mRS). We performed a generalized linear model and reported relative risks (RR) for smoking (adjustment for age, sex, hypertension, atrial fibrillation, stroke severity, time to EVT) in patient data stemming from the Virtual International Stroke Trials Archive-Endovascular database.Results Among 1,497 patients, 740(49.4%) were randomized to EVT; among EVT patients, 524(35.0%) received mechanical thrombectomy alone and 216(14.4%) received it in combination with IA-thrombolysis. Smokers (N = 396) had lower mRS scores (mean 2.9 vs. 3.2; p = 0.02) and mortality rates (10% vs. 17.3%; p<0.001) in univariate analysis. In all patients and in patients treated with mechanical thrombectomy alone, smoking had no effect on outcome in regression analyses. In patients who received IA-thrombolysis (N = 216;14%), smoking had an adjusted RR of 1.65 for an mRS1 (95%CI 0.77-3.55). Treatment with IA-thrombolysis itself led to reduced RR for favorable outcome (adjusted RR 0.30); interaction analysis of IA-thrombolysis and smoking revealed that non-smokers with IA-thrombolysis had mRS <= 2 in 47 cases (30%, adjusted RR 0.53 [0.41-0.69]) while smokers with IA-thrombolysis had mRS <= 2 in 23 cases (38%, adjusted RR 0.61 [0.42-0.87]).Conclusions Smokers had no clear clinical benefit from EVT that incorporates IA-thrombolysis.Clinical epidemiolog

Liver fibrosis indices and outcomes after primary intracerebral hemorrhage

Background and Purpose- Cirrhosis-clinically overt, advanced liver disease-is associated with an increased risk of hemorrhagic stroke and poor stroke outcomes. We sought to investigate whether subclinical liver disease, specifically liver fibrosis, is associated with clinical and radiological outcomes in patients with primary intracerebral hemorrhage. Methods- We performed a retrospective cohort study using data from the Virtual International Stroke Trials Archive-Intracerebral Hemorrhage. We included adult patients with primary intracerebral hemorrhage presenting within 6 hours of symptom onset. We calculated 3 validated fibrosis indices-Aspartate Aminotransferase-Platelet Ratio Index, Fibrosis-4 score, and Nonalcoholic Fatty Liver Disease Fibrosis Score-and modeled them as continuous exposure variables. Primary outcomes were admission hematoma volume and hematoma expansion. Secondary outcomes were mortality, and the composite of major disability or death, at 90 days. We used linear and logistic regression models adjusted for previously established risk factors. Results- Among 432 patients with intracerebral hemorrhage, the mean Aspartate Aminotransferase-Platelet Ratio Index, Fibrosis-4, and Nonalcoholic Fatty Liver Disease Fibrosis Score values on admission reflected intermediate probabilities of fibrosis, whereas standard hepatic assays and coagulation parameters were largely normal. After adjusting for potential confounders, Aspartate Aminotransferase-Platelet Ratio Index was associated with hematoma volume (β, 0.20 [95% CI, 0.04-0.36]), hematoma expansion (odds ratio, 1.6 [95% CI, 1.1-2.3]), and mortality (odds ratio, 1.8 [95% CI, 1.1-2.7]). Fibrosis-4 was also associated with hematoma volume (β, 0.27 [95% CI, 0.07-0.47]), hematoma expansion (odds ratio, 1.9 [95% CI, 1.2-3.0]), and mortality (odds ratio, 2.0 [95% CI, 1.1-3.6]). Nonalcoholic Fatty Liver Disease Fibrosis Score was not associated with any outcome. Indices were not associated with the composite of major disability or death. Conclusions- In patients with largely normal liver chemistries, 2 liver fibrosis indices were associated with admission hematoma volume, hematoma expansion, and mortality after intracerebral hemorrhage

Dependency and health utilities in stroke: data to inform cost-effectiveness analyses

Introduction: Health utilities (HU) assign preference weights to specific health states and are required for costeffectiveness analyses. Existing HU for stroke inadequately reflect the spectrum of post-stroke disability. Using international stroke trial data, we calculated HU stratified by disability to improve precision in future cost-effectiveness analyses. Materials and methods: We used European Quality of Life Score (EQ-5D-3L) data from the Virtual International Stroke Trials Archive (VISTA) to calculate HU, stratified by modified Rankin Scale scores (mRS) at 3 months. We applied published value sets to generate HU, and validated these using ordinary least squares regression, adjusting for age and baseline National Institutes of Health Stroke Scale (NIHSS) scores. Results: We included 3858 patients with acute ischemic stroke in our analysis (mean age: 67.5+-12.5, baseline NIHSS: 12+-5). We derived HU using value sets from 13 countries and observed significant international variation in HU distributions (Wilcoxon signed-rank test p<0.0001, compared with UK values). For mRS=0, mean HU ranged from 0.88 to 0.95; for mRS=5, mean HU ranged from -0.48 to 0.22. OLS regression generated comparable HU (for mRS=0, HU ranged from 0.9 to 0.95; for mRS=5, HU ranged from -0.33 to 0.15). Patients’ mRS scores at 3 months accounted for 65–71% of variation in the generated HU. Conclusion: We have generated HU stratified by dependency level, using a common trial endpoint, and describing expected variability when applying diverse value sets to an international population. These will improve future cost-effectiveness analyses. However, care should be taken to select appropriate value sets

Acute Blood Pressure and Outcome After Intracerebral Hemorrhage: The VISTA-ICH Cohort

BACKGROUND: Recent clinical trials suggest that it is safe to acutely lower systolic blood pressure (BP) to 140 mm Hg after ICH, but uncertainty remains regarding optimal management. We sought to better define the link between BP and outcome in ICH patients using data from the Virtual International Stroke Trials Archive (VISTA). METHODS: We performed a retrospective analysis of patients of the VISTA-ICH trials. We measured the strength of association between systolic and diastolic BP various components at different timepoints with unfavorable 3 month-outcome, defined as death or moderate-to-severe disability at 3 months (mRS of 4-6), after adjustment for known confounders. We also dichotomized BP values obtained at 24 h at different thresholds to better define an optimal treatment target. The association of BP with hematoma expansion (HE) was also analyzed. RESULTS: A total of 384 patients were included. Higher BP at 24 hours was associated with unfavorable outcome for systolic BP (OR 1.16, 95% C.I. 1.07-1.25), pulse pressure (OR 1.13, 95% C.I. 1.03-1.24), and diastolic BP (OR 1.11, 95% C.I. 1.01-1.23) per 10 mm Hg increment. The association between higher BP at 24 h and unfavorable outcome remained significant down to \u3e140 mm Hg. Elevated systolic BP at 24 h was also associated with HE (OR 1.11, 95% C.I. 1.02-1.21 per 10 mm Hg increment). CONCLUSION: Elevated BP after ICH at 24 h is associated with poor outcome. Our results support the practice of targeting a systolic BP of 140 mm Hg

Stroke aetiological classification reliability and effect on trial sample size: systematic review, meta-analysis and statistical modelling.

BACKGROUND: Inter-observer variability in stroke aetiological classification may have an effect on trial power and estimation of treatment effect. We modelled the effect of misclassification on required sample size in a hypothetical cardioembolic (CE) stroke trial. METHODS: We performed a systematic review to quantify the reliability (inter-observer variability) of various stroke aetiological classification systems. We then modelled the effect of this misclassification in a hypothetical trial of anticoagulant in CE stroke contaminated by patients with non-cardioembolic (non-CE) stroke aetiology. Rates of misclassification were based on the summary reliability estimates from our systematic review. We randomly sampled data from previous acute trials in CE and non-CE participants, using the Virtual International Stroke Trials Archive. We used bootstrapping to model the effect of varying misclassification rates on sample size required to detect a between-group treatment effect across 5000 permutations. We described outcomes in terms of survival and stroke recurrence censored at 90 days. RESULTS: From 4655 titles, we found 14 articles describing three stroke classification systems. The inter-observer reliability of the classification systems varied from 'fair' to 'very good' and suggested misclassification rates of 5% and 20% for our modelling. The hypothetical trial, with 80% power and alpha 0.05, was able to show a difference in survival between anticoagulant and antiplatelet in CE with a sample size of 198 in both trial arms. Contamination of both arms with 5% misclassified participants inflated the required sample size to 237 and with 20% misclassification inflated the required sample size to 352, for equivalent trial power. For an outcome of stroke recurrence using the same data, base-case estimated sample size for 80% power and alpha 0.05 was n = 502 in each arm, increasing to 605 at 5% contamination and 973 at 20% contamination. CONCLUSIONS: Stroke aetiological classification systems suffer from inter-observer variability, and the resulting misclassification may limit trial power. TRIAL REGISTRATION: Protocol available at reviewregistry540

β-Blockers, Pneumonia, and Outcome After Ischemic Stroke: Evidence From Virtual International Stroke Trials Archive

Increased sympathetic drive after stroke is involved in the pathophysiology of several complications including poststroke immunudepression. β-Blocker (BB) therapy has been suggested to have neuroprotective properties and to decrease infectious complications after stroke. We aimed to examine the effects of random pre- and on-stroke BB exposure on mortality, functional outcome, and occurrence of pneumonia after ischemic stroke. Data including standard demographic and clinical variables as well as prestroke and on-stroke antihypertensive medication, incidence of pneumonia, functional outcome defined using modified Rankin Scale and mortality at 3 months were extracted from the Virtual International Stroke Trials Archive. For statistical analysis multivariable Poisson regression was used. In total, 5212 patients were analyzed. A total of 1155 (22.2%) patients were treated with BB before stroke onset and 244 (4.7%) patients were newly started with BB in the acute phase of stroke. Mortality was 17.5%, favorable outcome (defined as modified Rankin Scale, 0-2) occurred in 58.2% and pneumonia in 8.2% of patients. Prestroke BB showed no association with mortality. On-stroke BB was associated with reduced mortality (adjusted risk ratio, 0.63; 95% confidence interval, 0.42-0.96). Neither prestroke BB nor on-stroke BB showed an association with functional outcome. Both prestroke and on-stroke BB were associated with reduced frequency of pneumonia (adjusted risk ratio, 0.77; 95% confidence interval, 0.6-0.98 and risk ratio, 0.49; 95% confidence interval, 0.25-0.95). In this large nonrandomized comparison, on-stroke BB was associated with reduced mortality. Prestroke and on-stroke BB were inversely associated with incidence of nosocomial pneumonia. Randomized trials investigating the potential of β-blockade in acute stroke may be warranted