Effect of definition and methods on estimates of prevalence of large vessel occlusion in acute ischemic stroke: a systematic review and meta-analysis

Introduction Accurate estimation of the incidence of large vessel occlusion (LVO) is critical for planning stroke systems of care and approximating workforce requirements. This systematic review aimed to estimate the prevalence of LVO among patients with acute ischemic stroke (AIS), with emphasis on definitions and methods used by different studies. Methods A systematic literature review was performed to search for articles on the prevalence of LVO and AIS. All articles describing the frequency of LVO frequency among AIS patients were included. Studies without consecutive recruitment or confirmation of LVO with CT angiography or MR angiography were excluded. Heterogeneity of the studies was assessed; meta-regression was performed to estimate the effect of LVO definition and study methods on LVO prevalence. Results 18 articles met the inclusion criteria: 5 studies presented population based estimates; 13 provided single hospital experiences (5 prospective, 8 retrospective). The AIS denominator (number of all AIS) from which LVO rates were generated was variable. Nine different definitions were used, based on occlusion site. Significant heterogeneity existed among the studies (I 2 =99%, P<0.001). The prevalence of LVO among patients with suspected AIS ranged from 13% to 52%. Overall prevalence was 30.0% (95% CI 25.0% to 35.0%). Pooled prevalence of LVO among suspected AIS patients was 21% (95% CI 19% to 30%). Based on meta-regression, the method of AIS denominator determination significantly influenced heterogeneity (P=0.018). Conclusion The heterogeneity of LVO estimates was remarkably high. The method of AIS denominator determination was the most significant predictor of LVO estimates. Studies with a standardized LVO definition and methods of AIS estimation are necessary to estimate the true prevalence of LVO among patients with AIS.