Supplementary Material for: Variation in ischemic stroke payments in the USA: a Medicare beneficiary study

Introduction: The growing cost of stroke care has created the need for outcome-oriented and cost-saving payment models. Identifying imbalances in the current reimbursement model is an essential step towards designing impactful value-based reimbursement strategies. This study describes the variation in reimbursement fees for ischemic stroke management across the United States. Methods: This Medicare Fee-For-Service claims study examines USA beneficiaries who suffered an ischemic stroke from 2021Q1 to 2022Q2 identified using the Medicare Severity Diagnosis-Related Groups (MS-DRGs). Demographic national and regional US data were extracted from the Census Bureau. The MS-DRG codes were grouped into four categories according to treatment modality and clinical complexity. Our primary outcome of interest was payments made across individual US states and US geographic regions, assessed by computing the mean incremental payment in cases of comparable complexity. Differences between states for each MS-DRG were statistically evaluated using a linear regression model of the logarithmic transformed payments. Results: 227,273 ischemic stroke cases were included in our analysis. Significant variations were observed among all DRG-groups defined by medical complexity, treatment modality, and states (p<0.001). Differences in mean payment per case with the same MS-DRG vary by as high as 500% among individual states. Although higher payment rates were observed in MS-DRG codes with Major Comorbidities or Complexity, the variation was more expressive for codes without MCC. It was not possible to identify a standard mean incremental fee at a state level. At a regional level, the Northeast registered the highest fees, followed by the West, Midwest, and South, which correlates with poverty rates and median household income in the regions. Discussion/Conclusions: The payment variability observed across USA states suggests that the current reimbursement system needs to be aligned with stroke treatment costs. Future studies may go one step further to evaluate accurate stroke management costs to guide policymakers in introducing health policies that promote better care for stroke patients.

引言：卒中护理成本日益攀升，催生了对以结局为导向且能节约成本的付费模式的迫切需求。明确当前付费模式存在的失衡问题，是设计具有影响力的基于价值的付费策略的关键步骤。本研究探讨了美国境内缺血性卒中管理相关报销费用的差异。
方法：本项基于医疗保险按服务收费（Medicare Fee-For-Service）的索赔研究，选取2021年第一季度至2022年第二季度期间罹患缺血性卒中的美国医疗保险受益人群，通过医疗保险严重程度诊断相关分组（Medicare Severity Diagnosis-Related Groups, MS-DRGs）进行病例识别。美国全国及区域人口统计数据取自美国人口普查局（Census Bureau）。依据治疗方式与临床复杂性，将MS-DRG编码划分为四大类别。本研究的主要观察结局为美国各州及地理区域的支付金额，通过计算相同复杂性病例的平均增量支付额进行评估。针对每个MS-DRG的州间差异，采用对数转换支付额的线性回归模型进行统计学检验。
结果：本研究共纳入227273例缺血性卒中病例。在按医疗复杂性、治疗方式划分的所有DRG组别以及各州之间，均观察到显著差异（p<0.001）。同一MS-DRG的单病例平均支付额在各州间的差异最高可达500%。尽管伴有主要合并症或复杂性较高的MS-DRG编码对应更高的支付费率，但无主要合并症（Major Comorbidities or Complexity, MCC）的编码组间差异更为显著。无法在州级层面确定统一的平均增量费用。在区域层面，东北部地区的收费最高，其次为西部、中西部与南部，这与各区域的贫困率及家庭收入中位数呈相关性。
讨论与结论：美国各州间存在的支付差异表明，当前的报销体系需与卒中治疗成本相匹配。未来的研究可进一步精准评估卒中管理的实际成本，以辅助政策制定者出台能够改善卒中患者诊疗质量的卫生政策。