Loesment-Wendelmuth Amina, Schaeffner Elke, Ebert Natalie
Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany.
Institute of Public, Charité - Universitätsmedizin Berlin, Seestrasse 73, Haus 10, D-13347, Berlin, Germany.
BMC Nephrol. 2017 Mar 14;18(1):87. doi: 10.1186/s12882-017-0508-7.
Serum creatinine concentration (Scr) and creatinine based GFR estimating equations (eGFR) are commonly used as an estimate of GFR. However, serum creatinine concentration is also influenced by non-GFR determinants. This case report presents two elderly patients with normal Scr but elevated serum cystatin C concentration (Scys) where the exclusive assessment of Scr would have lead to an overestimation of GFR and would have misclassified the patients as having a normal kidney function.
Patient 1, a 102-year-old woman, presented with a Scr of 0.45 mg/dl, while her Scys was elevated (1.55 mg/l). Depending on which of the five GFR estimating equations was used, the patient could be classified into four different CKD-Stages (2, 3a, 3b and 4). The largest difference between the eGFR-results was 94 ml/min/1.73 m (Δ-eGFR). Patient 2, an 88-year-old man, also had normal Scr (0.93 mg/dl) but elevated Scys (1.55 mg/l). An iohexol clearance measurement yielded a measured GFR (mGFR) of 44 ml/min/1.73 m. Four out of five GFR equations would have overestimated the patient's kidney function.
The presented cases highlight the influence of non-GFR determinants on Scr and demonstrate the variability of eGFR results depending on the filtration marker and GFR equation used. Especially for older adults, it shows the great clinical importance of understanding the limitations of each filtration marker and of identifying situations in which relying on eGFR alone can lead to false estimation of kidney function. In these situations, cysC based GFR equations may provide improved accuracy of GFR assessment and may protect patients from drug overdosing and the abundant use of contrast agents.
血清肌酐浓度（Scr）和基于肌酐的肾小球滤过率估算方程（eGFR）通常被用作肾小球滤过率的估算指标。然而，血清肌酐浓度也受非肾小球滤过率决定因素的影响。本病例报告介绍了两名老年患者，其Scr正常但血清胱抑素C浓度（Scys）升高，仅评估Scr会导致肾小球滤过率高估，并会将患者错误分类为肾功能正常。
患者1，一名102岁女性，Scr为0.45mg/dl，而Scys升高（1.55mg/l）。根据使用的五个肾小球滤过率估算方程中的哪一个，该患者可被分类为四个不同的慢性肾脏病阶段（2、3a、3b和4）。eGFR结果之间的最大差异为94ml/min/1.73m²（Δ-eGFR）。患者2，一名88岁男性，Scr也正常（0.93mg/dl）但Scys升高（1.55mg/l）。碘海醇清除率测量得出的实测肾小球滤过率（mGFR）为44ml/min/1.73m²。五个肾小球滤过率方程中有四个会高估该患者的肾功能。
所呈现的病例突出了非肾小球滤过率决定因素对Scr的影响，并证明了eGFR结果因所使用的滤过标志物和肾小球滤过率方程而异。特别是对于老年人，这显示了理解每个滤过标志物的局限性以及识别仅依赖eGFR可能导致肾功能错误估计的情况的重大临床意义。在这些情况下，基于胱抑素C的肾小球滤过率方程可能会提高肾小球滤过率评估的准确性，并可能使患者避免药物过量和造影剂的大量使用。
