Larsson Anders, Akerstedt Torbjörn, Hansson Lars-Olof, Axelsson John
Section of Clinical Chemistry, Department of Medical Sciences, Uppsala University, Uppsala, Sweden.
Chronobiol Int. 2008 Nov;25(6):1047-61. doi: 10.1080/07420520802553614.
The estimation of the glomerular filtration rate (GFR) is essential for the evaluation of patients with kidney disease and for the treatment of patients with medications that are eliminated by the kidneys. Plasma cystatin C has been shown in several studies to be superior to plasma creatinine for the estimation of GFR. However, there is limited information on the circadian variation of cystatin C and estimated GFR using cystatin C (eGFR(CystC)) or "The Modification of Diet in Renal Disease Study" (MDRD) (eGFR(MDRD)) equations. We studied the circadian variation of cystatin C and creatinine during night- and day-sleep conditions in seven healthy volunteers. Serum samples were collected every hour (48 samples per individual) to evaluate the effect of different sampling times on the test results. The median intra-individual coefficients of variations for the studied markers were 4.2% for creatinine, 4.7% for eGFR(MDRD), 5.5% for cystatin C, and 7.7% for eGFR(CystC). Neither cystatin C nor creatinine differed significantly between the night- and day-sleep conditions. Cystatin C differed significantly with time of day (p=.0003), but this was not the case for creatinine (p=.11). The circadian variation of cystatin C was minor. Small but significant increases in creatinine values and a decrease of eGFR(MDRD) were observed after food intake. Thus, cystatin C and creatinine sampling does not have to be restricted to specific times of the day.
肾小球滤过率（GFR）的估算对于评估肾病患者以及使用经肾脏排泄的药物治疗患者至关重要。多项研究表明，血浆胱抑素C在估算GFR方面优于血浆肌酐。然而，关于胱抑素C的昼夜变化以及使用胱抑素C估算的GFR（eGFR(CystC)）或“肾脏病饮食改良研究”（MDRD）估算的GFR（eGFR(MDRD)）方程的信息有限。我们研究了7名健康志愿者在夜间和日间睡眠条件下胱抑素C和肌酐的昼夜变化。每小时采集血清样本（每人48个样本），以评估不同采样时间对检测结果的影响。所研究指标的个体内变异系数中位数分别为：肌酐4.2%，eGFR(MDRD) 4.7%，胱抑素C 5.5%，eGFR(CystC) 7.7%。夜间和日间睡眠条件下，胱抑素C和肌酐均无显著差异。胱抑素C随时间有显著差异（p = 0.0003），但肌酐并非如此（p = 0.11）。胱抑素C的昼夜变化较小。进食后观察到肌酐值有小幅但显著的升高以及eGFR(MDRD)下降。因此，胱抑素C和肌酐的采样不必局限于一天中的特定时间。
