Center for Stroke Research Berlin, Charité - Universitätsmedizin Berlin, Berlin, Germany.
Institute of Public Health, Charité - Universitätsmedizin Berlin, Berlin, Germany.
Eur Stroke J. 2023 Mar;8(1):370-379. doi: 10.1177/23969873221149464. Epub 2023 Jan 13.
Modified Rankin Scale (mRS) scores are used to measure functional outcomes after stroke. Researchers create horizontal stacked bar graphs (nicknamed "Grotta bars") to illustrate distributional differences in scores between groups. In well-conducted randomized controlled trials, Grotta bars have a causal interpretation. However, the common practice of exclusively presenting unadjusted Grotta bars in observational studies can be misleading in the presence of confounding. We demonstrated this problem and a possible solution using an empirical comparison of 3-month mRS scores among stroke/TIA patients discharged home versus elsewhere after hospitalization.
Using data from the Berlin-based B-SPATIAL registry, we estimated the probability of being discharged home conditional on prespecified measured confounding factors and generated stabilized inverse probability of treatment (IPT) weights for each patient. We visualized mRS distributions by group with Grotta bars for the IPT-weighted population in which measured confounding was removed. We then used ordinal logistic regression to quantify unadjusted and adjusted associations between being discharged home and the 3-month mRS score.
Of 3184 eligible patients, 2537 (79.7%) were discharged home. In the unadjusted analyses, those discharged home had considerably lower mRS compared with patients discharged elsewhere (common odds ratio, cOR = 0.13, 95% CI: 0.11-0.15). After removing measured confounding, we obtained substantially different mRS distributions, visually apparent in the adjusted Grotta bars. No statistically significant association was found after confounding adjustment (cOR = 0.82, 95% CI: 0.60-1.12).
The practice of presenting only unadjusted stacked bar graphs for mRS scores together with adjusted effect estimates in observational studies can be misleading. IPT weighting can be implemented to create Grotta bars that account for measured confounding, which are more consistent with the presentation of adjusted results in observational studies.
改良 Rankin 量表（mRS）评分用于衡量卒中后的功能结局。研究人员创建水平堆叠条形图（俗称“Grotta 条形图”）来展示组间评分的分布差异。在精心设计的随机对照试验中，Grotta 条形图具有因果解释。然而，在存在混杂的情况下，观察性研究中仅呈现未经调整的 Grotta 条形图的常见做法可能具有误导性。我们使用卒中/TIA 患者住院后出院回家与其他地方之间的 3 个月 mRS 评分的实证比较，展示了这个问题和一种可能的解决方案。
我们使用柏林 B-SPATIAL 注册中心的数据，根据预设的测量混杂因素估计了出院回家的概率，并为每位患者生成了稳定的治疗逆概率（IPT）权重。我们使用 Grotta 条形图可视化了 IPT 加权人群中组间的 mRS 分布，其中去除了测量混杂。然后，我们使用有序逻辑回归量化了出院回家与 3 个月 mRS 评分之间未经调整和调整后的关联。
在 3184 名合格患者中，2537 名（79.7%）出院回家。在未调整的分析中，出院回家的患者 mRS 评分明显低于其他出院地点的患者（常见比值比，cOR=0.13，95%CI：0.11-0.15）。在去除测量混杂后，我们获得了明显不同的 mRS 分布，在调整后的 Grotta 条形图中可以明显看出。混杂调整后，没有发现统计学上显著的关联（cOR=0.82，95%CI：0.60-1.12）。
在观察性研究中，仅呈现未经调整的堆叠条形图和调整后的效应估计值来表示 mRS 评分可能具有误导性。可以实施 IPT 加权来创建考虑测量混杂的 Grotta 条形图，这与观察性研究中调整后的结果呈现更一致。
