Supplementary Material for: Impact of ‘Black Race’ Coefficient in eGFR on Our Community and Medical Education

Introduction: The use of race in estimation of glomerular filtration rate (eGFR) started a critical national conversation on numerous areas of medicine touched by racism; with a call for removal of race from calculation of eGFR. We scrutinized use of ‘Black race’ coefficient in MDRD eGFR calculation and consequence of its use on our local community in SW Michigan. Methods: A cross-sectional analysis of de-identified electronic health record (EHR) data from routine outpatient primary care visits, from 1/1/2019 to 12/31/2019 included variables such as age, race, gender, serum creatinine levels and calculated eGFRs (if any), using Chi-square tests for association and Wald-approximation 95% confidence interval. During the data collection period in 2019, both hospital systems and the outpatient clinic site were all using MDRD. Results: eGFR and associated CKD stage were calculated for 131,863 patients. Chi-square tests found significant differences in rates of CKD stages 3,4 and 5 between ‘Black’ and ‘not Black’. And, the 95% confidence interval for the proportion of Black patients who would advance to the next stage of CKD upon ignoring ‘Black race’ (using Wald-approximated Confidence Interval for binomial proportion) is between 41.1% and 43.0%. Discussion: The eGFR calculations which place Black patients in lower CKD stages initially may deprive them of important treatment and referral early in their disease course. Removal of the Black race coefficient allows for referral to a nephrologist, Medicare coverage, and the potential need for transplant and/or dialysis. Conclusion: Our analysis demonstrates the impact removal of ‘black race’ coefficient from MDRD eGFR calculation could have on our community.

引言：估算肾小球滤过率（estimated glomerular filtration rate，eGFR）计算中引入种族因素，在受种族主义影响的诸多医学领域引发了一场极具争议的全国性讨论，各界呼吁在eGFR的计算中剔除种族相关变量。本研究针对肾脏病饮食改良（MDRD）eGFR计算公式中“黑人种族”系数的使用情况，以及该系数对密歇根州西南部本地人群的影响展开了详细审视。

方法：本研究对2019年1月1日至2019年12月31日期间常规门诊初级保健就诊的去标识化电子健康档案（Electronic Health Record，EHR）数据开展横断面分析，纳入年龄、种族、性别、血清肌酐水平及已计算的eGFR（若有）等变量；采用卡方检验分析变量间关联性，并使用Wald近似法计算95%置信区间。在2019年的数据收集阶段，本研究涉及的所有医院系统及门诊诊所均采用MDRD公式进行eGFR计算。

结果：本研究为131863名患者计算了eGFR及对应的慢性肾脏病（Chronic Kidney Disease，CKD）分期。卡方检验结果显示，“黑人”与“非黑人”人群的CKD3、4、5期患病率存在显著差异。在忽略“黑人种族”系数的情况下，黑人患者进展至下一CKD分期的比例的95%置信区间（采用二项分布比例的Wald近似置信区间计算）为41.1%~43.0%。

讨论：最初将黑人患者归类为较低CKD分期的eGFR计算方式，可能导致他们在疾病早期错失重要的治疗与转诊机会。剔除黑人种族系数后，患者可获得肾病专科转诊、联邦医疗保险（Medicare）覆盖，以及肾移植或透析的潜在救治机会。

结论：本研究分析证实，从MDRD的eGFR计算中剔除“黑人种族”系数，会对本地区人群产生切实影响。