• Stroke

We appreciate the letter from Zheng et al1 suggesting that the random effects model, not the fixed effects model, should be used to pool the results for our meta-analysis.2 In a sensitivity test, pooled results from the random effects model did not significantly show that endovascular therapy (EVT) compared with best medical management was associated with a higher rate of being disability free for patients with acute ischemic stroke (AIS) with National Institutes of Health Stroke Scale (NIHSS) scores of ≤5 due to proximal internal carotid artery (ICA) or middle cerebral artery M1 occlusions. However, the main point of this meta-analysis was to highlight the importance of knowledge about specific vessel occlusion sites in decision making for AIS with NIHSS scoresof ≤5 due to vessel occlusions in the anterior circulation, and the results obtained from the random effects model were consistent with the results obtained from the fixed effects model, as shown in the results and in the online supplemental eFigure 1 (random effects model: proximal ICA or M1 occlusions, OR 1.68, 95% CI 0.98 to 2.88 vs distal M2 occlusions, OR 0.69, 95% CI 0.48 to 1.00; p for interaction=0.008, I²=86%).2 However, these observational data should only be seen as suggestive, and the findings of two ongoing trials will provide robust evidence for the efficacy of EVT in mild AIS with proximal ICA or M1 occlusions.3 4 On the other hand, the study design of these two ongoing trials,3 4 of not enrolling patients with mild AIS with pure distal M2 occlusions, may be based on the assumption that EVT is not likely to be beneficial in these patients, which was confirmed by the current meta-analysis.

The study design and purpose of observational studies may vary substantially. The Newcastle–Ottawa Scale includes components of sequence generation, allocation sequence concealment, blinding, incomplete outcome data, selective outcome reporting, and other potential sources of bias, and is an ideal tool to evaluate the quality of epidemiological studies. However, whether the Newcastle–Ottawa Scale was the only appropriate tool to evaluate EVT studies for mild AIS due to vessel occlusions might not be clear.

Based on the pooled results from either the fixed effects model or the random effects model of this meta-analysis, EVT could be considered as a treatment option for mild AIS patients due to proximal ICA or M1 occlusions but it may be imprudent to use EVT in patients with mild AIS due to distal M2 occlusions.