Beckstead Alexander, Holmes H Reed, Tran Vi, Dass Bhagwan
Family Medicine Residency, Eglin Air Force Base, Florida.
Department of Internal Medicine, University of Florida, Gainesville.
Fed Pract. 2024 Feb;41(2):62-66. doi: 10.12788/fp.0440. Epub 2024 Feb 12.
Independent of age, sex, and body composition, individuals of African American race and individuals with high muscle mass have elevated serum creatinine (sCr) levels on average that may result in overestimation of chronic kidney disease (CKD). We present a misdiagnosed case of CKD based on sCr levels, illustrating the utility of cystatin C (CysC) confirmation testing to answer the question: Can confirmation screening of kidney function with CysC in African American patients and patients with high muscle mass reduce the misdiagnosis of CKD?
A 35-year-old African American man with a history of well-controlled HIV was found to have consistently elevated creatinine (Cr). We diagnosed CKD stage 3A based on the estimated glomerular filtration rate (eGFR). Further evaluation showed isolated elevation of sCr with unremarkable urinalysis and other laboratory tests. sCr elevation predated diagnosis and HIV treatment. A CysC-based eGFR (eGFR) test confirmed the absence of CKD.
The 2009 CKD Epidemiology Collaboration calculation of eGFR based on sCr concentration uses age, sex, and race, with an updated recommendation in 2021 to exclude race. Both equations are less accurate in African American patients, individuals taking medications that interfere with sCr secretion and assay, and patients taking creatine supplements or high protein intake. These clinical scenarios decrease sCr-based eGFR (eGFR) but do not change measured eGFR or eGFR. Using sCr and serum cystatin C (eGFR) yields better concordance to measured eGFR across all races than does eGFR estimation based on Cr alone. Confirmation with CysC can avoid misdiagnosis, incorrect dosing of drugs, and inaccurate representation of the fitness for duty.
独立于年龄、性别和身体成分之外，非裔美国人以及肌肉量高的个体平均血清肌酐（sCr）水平升高，这可能导致对慢性肾脏病（CKD）的高估。我们报告一例基于sCr水平误诊CKD的病例，说明胱抑素C（CysC）确认检测在回答以下问题方面的效用：对非裔美国患者和肌肉量高的患者进行CysC肾功能确认筛查能否减少CKD的误诊？
一名35岁有HIV病史且病情控制良好的非裔美国男性，其肌酐（Cr）持续升高。根据估算的肾小球滤过率（eGFR），我们诊断为CKD 3A期。进一步评估显示sCr单独升高，尿液分析和其他实验室检查无异常。sCr升高早于诊断和HIV治疗。基于CysC的eGFR检测证实不存在CKD。
2009年CKD流行病学协作组基于sCr浓度计算eGFR时使用年龄、性别和种族因素，2021年更新建议排除种族因素。这两个公式在非裔美国患者、服用干扰sCr分泌和检测的药物的个体以及服用肌酸补充剂或高蛋白饮食的患者中准确性较低。这些临床情况会降低基于sCr的eGFR，但不会改变实测eGFR或CysC估算的eGFR。与仅基于Cr估算eGFR相比，使用sCr和血清胱抑素C（eGFR）在所有种族中与实测eGFR的一致性更好。用CysC进行确认可以避免误诊、药物剂量错误以及对工作适应性的不准确评估。
