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      Antiplatelet regimens in the long-term secondary prevention of transient ischaemic attack and ischaemic stroke: an updated network meta-analysis

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          Abstract

          Objective

          To examine the comparative efficacy and safety of different antiplatelet regimens in patients with prior non-cardioembolic ischaemic stroke or transient ischaemic attack.

          Design

          Systematic review and network meta-analysis.

          Data sources

          As on 31 March 2015, all randomised controlled trials that investigated the effects of antiplatelet agents in the long-term (≥3 months) secondary prevention of non-cardioembolic transient ischaemic attack or ischaemic stroke were searched and identified.

          Outcome measures

          The primary outcome measure of efficacy was serious vascular events (non-fatal stroke, non-fatal myocardial infarction and vascular death). The outcome measure of safety was any bleeding.

          Results

          A total of 36 randomised controlled trials (82 144 patients) were included. Network meta-analysis showed that cilostazol was significantly more effective than clopidogrel (OR 0.77, 95% credible interval 0.60–0.98) and low-dose (75–162 mg daily) aspirin (0.69, 0.55–0.86) in the prevention of serious vascular events. Aspirin (50 mg daily) plus dipyridamole (400 mg daily) and clopidogrel reduced the risk of serious vascular events compared with low-dose aspirin; however, the difference was not statistically significant. Furthermore, low-dose aspirin was as effective as higher daily doses. Cilostazol was associated with a significantly lower bleeding risk than most of the other regimens. Moreover, aspirin plus clopidogrel was associated with significantly more haemorrhagic events than other regimens. Direct comparisons showed similar results as the network meta-analysis.

          Conclusions

          Cilostazol was significantly more effective than aspirin and clopidogrel alone in the long-term prevention of serious vascular events in patients with prior non-cardioembolic ischaemic stroke or transient ischaemic attack. Cilostazol was associated with a significantly lower bleeding risk than low-dose aspirin (75–162 mg daily) and aspirin (50 mg daily) plus dipyridamole (400 mg daily). Low-dose aspirin was as effective as higher daily doses. However, further large, randomised, controlled, head-to-head trials are needed, especially in non-Asian ethnic groups.

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          Most cited references50

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          Collaborative meta-analysis of randomised trials of antiplatelet therapy for prevention of death, myocardial infarction, and stroke in high risk patients.

          (2002)
          To determine the effects of antiplatelet therapy among patients at high risk of occlusive vascular events. Collaborative meta-analyses (systematic overviews). Randomised trials of an antiplatelet regimen versus control or of one antiplatelet regimen versus another in high risk patients (with acute or previous vascular disease or some other predisposing condition) from which results were available before September 1997. Trials had to use a method of randomisation that precluded prior knowledge of the next treatment to be allocated and comparisons had to be unconfounded-that is, have study groups that differed only in terms of antiplatelet regimen. 287 studies involving 135 000 patients in comparisons of antiplatelet therapy versus control and 77 000 in comparisons of different antiplatelet regimens. "Serious vascular event": non-fatal myocardial infarction, non-fatal stroke, or vascular death. Overall, among these high risk patients, allocation to antiplatelet therapy reduced the combined outcome of any serious vascular event by about one quarter; non-fatal myocardial infarction was reduced by one third, non-fatal stroke by one quarter, and vascular mortality by one sixth (with no apparent adverse effect on other deaths). Absolute reductions in the risk of having a serious vascular event were 36 (SE 5) per 1000 treated for two years among patients with previous myocardial infarction; 38 (5) per 1000 patients treated for one month among patients with acute myocardial infarction; 36 (6) per 1000 treated for two years among those with previous stroke or transient ischaemic attack; 9 (3) per 1000 treated for three weeks among those with acute stroke; and 22 (3) per 1000 treated for two years among other high risk patients (with separately significant results for those with stable angina (P=0.0005), peripheral arterial disease (P=0.004), and atrial fibrillation (P=0.01)). In each of these high risk categories, the absolute benefits substantially outweighed the absolute risks of major extracranial bleeding. Aspirin was the most widely studied antiplatelet drug, with doses of 75-150 mg daily at least as effective as higher daily doses. The effects of doses lower than 75 mg daily were less certain. Clopidogrel reduced serious vascular events by 10% (4%) compared with aspirin, which was similar to the 12% (7%) reduction observed with its analogue ticlopidine. Addition of dipyridamole to aspirin produced no significant further reduction in vascular events compared with aspirin alone. Among patients at high risk of immediate coronary occlusion, short term addition of an intravenous glycoprotein IIb/IIIa antagonist to aspirin prevented a further 20 (4) vascular events per 1000 (P<0.0001) but caused 23 major (but rarely fatal) extracranial bleeds per 1000. Aspirin (or another oral antiplatelet drug) is protective in most types of patient at increased risk of occlusive vascular events, including those with an acute myocardial infarction or ischaemic stroke, unstable or stable angina, previous myocardial infarction, stroke or cerebral ischaemia, peripheral arterial disease, or atrial fibrillation. Low dose aspirin (75-150 mg daily) is an effective antiplatelet regimen for long term use, but in acute settings an initial loading dose of at least 150 mg aspirin may be required. Adding a second antiplatelet drug to aspirin may produce additional benefits in some clinical circumstances, but more research into this strategy is needed.
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            A randomised, blinded, trial of clopidogrel versus aspirin in patients at risk of ischaemic events (CAPRIE). CAPRIE Steering Committee.

            (1996)
            Many clinical trials have evaluated the benefit of long-term use of antiplatelet drugs in reducing the risk of clinical thrombotic events. Aspirin and ticlopidine have been shown to be effective, but both have potentially serious adverse effects. Clopidogrel, a new thienopyridine derivative similar to ticlopidine, is an inhibitor of platelet aggregation induced by adenosine diphosphate. CAPRIE was a randomised, blinded, international trial designed to assess the relative efficacy of clopidogrel (75 mg once daily) and aspirin (325 mg once daily) in reducing the risk of a composite outcome cluster of ischaemic stroke, myocardial infarction, or vascular death; their relative safety was also assessed. The population studied comprised subgroups of patients with atherosclerotic vascular disease manifested as either recent ischaemic stroke, recent myocardial infarction, or symptomatic peripheral arterial disease. Patients were followed for 1 to 3 years. 19,185 patients, with more than 6300 in each of the clinical subgroups, were recruited over 3 years, with a mean follow-up of 1.91 years. There were 1960 first events included in the outcome cluster on which an intention-to-treat analysis showed that patients treated with clopidogrel had an annual 5.32% risk of ischaemic stroke, myocardial infarction, or vascular death compared with 5.83% with aspirin. These rates reflect a statistically significant (p = 0.043) relative-risk reduction of 8.7% in favour of clopidogrel (95% Cl 0.3-16.5). Corresponding on-treatment analysis yielded a relative-risk reduction of 9.4%. There were no major differences in terms of safety. Reported adverse experiences in the clopidogrel and aspirin groups judged to be severe included rash (0.26% vs 0.10%), diarrhoea (0.23% vs 0.11%), upper gastrointestinal discomfort (0.97% vs 1.22%), intracranial haemorrhage (0.33% vs 0.47%), and gastrointestinal haemorrhage (0.52% vs 0.72%), respectively. There were ten (0.10%) patients in the clopidogrel group with significant reductions in neutrophils (< 1.2 x 10(9)/L) and 16 (0.17%) in the aspirin group. Long-term administration of clopidogrel to patients with atherosclerotic vascular disease is more effective than aspirin in reducing the combined risk of ischaemic stroke, myocardial infarction, or vascular death. The overall safety profile of clopidogrel is at least as good as that of medium-dose aspirin.
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              Evaluation of inconsistency in networks of interventions.

              The assumption of consistency, defined as agreement between direct and indirect sources of evidence, underlies the increasingly popular method of network meta-analysis. No evidence exists so far regarding the extent of inconsistency in full networks of interventions or the factors that control its statistical detection. In this paper we assess the prevalence of inconsistency from data of 40 published networks of interventions involving 303 loops of evidence. Inconsistency is evaluated in each loop by contrasting direct and indirect estimates and by employing an omnibus test of consistency for the entire network. We explore whether different effect measures for dichotomous outcomes are associated with differences in inconsistency, and evaluate whether different ways to estimate heterogeneity affect the magnitude and detection of inconsistency. Inconsistency was detected in from 2% to 9% of the tested loops, depending on the effect measure and heterogeneity estimation method. Loops that included comparisons informed by a single study were more likely to show inconsistency. About one-eighth of the networks were found to be inconsistent. The proportions of inconsistent loops do not materially change when different effect measures are used. Important heterogeneity or the overestimation of heterogeneity was associated with a small decrease in the prevalence of statistical inconsistency. The study suggests that changing the effect measure might improve statistical consistency, and that an analysis of sensitivity to the assumptions and an estimator of heterogeneity might be needed before reaching a conclusion about the absence of statistical inconsistency, particularly in networks with few studies.
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                Author and article information

                Journal
                BMJ Open
                BMJ Open
                bmjopen
                bmjopen
                BMJ Open
                BMJ Publishing Group (BMA House, Tavistock Square, London, WC1H 9JR )
                2044-6055
                2016
                17 March 2016
                : 6
                : 3
                : e009013
                Affiliations
                Department of Neurology, Neuroscience Center, The First Hospital of Jilin University , Changchun, Jilin, China
                Author notes
                [Correspondence to ] Professor Yi Yang; doctoryangyi@ 123456163.com
                Article
                bmjopen-2015-009013
                10.1136/bmjopen-2015-009013
                4800132
                26988347
                665b68a6-a22b-413a-9617-d86e257db5c7
                Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

                This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/

                History
                : 8 June 2015
                : 12 February 2016
                : 17 February 2016
                Categories
                Neurology
                Research
                1506
                1713
                1694
                1723

                Medicine
                cerebral infarction,meta-analysis,platelet aggregation inhibitors,secondary prevention,transient ischemic attack

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