Glomerular filtration rate (GFR) is the best indicator of renal function. The gold standard for GFR measurement is inulin clearance. However, its measurement is inconvenient, time-consuming, and costly. Thus, in both scientific studies and routine clinical practice nuclear medicine methods ((99m)Tc-diethylenetriaminepentaacetic acid [(99m)Tc-DTPA] and (51)Cr-ethylenediaminetetraacetic acid [(51)Cr-EDTA]) are preferred, and they correlate strongly with inulin clearance. In addition, cystatin C and β-trace protein have also recently been used for this purpose. In the literature, however, data are limited about the clinical value of cystatin C and β-trace protein in GFR measurement in chronic renal disease (CRD), and the results have been inconclusive. In this study, we aimed to determine the efficiency of cystatin C and β-trace protein in the determination of GFR in CRD patients.
Methods: Eighty-four patients with CRD were included in the study (59 men and 25 women; age range, 21-88 y; mean age, 61 y). GFR was calculated using the gold-standard (99m)Tc-DTPA 2-sample plasma sampling method (TPSM) and 2 alternative methods: a formula using cystatin C and a formula using β-trace protein. The correlation between TPSM and the cystatin C and β-trace protein methods was assessed, and Bland-Altman analysis was used to graph scatterplots of the differences at a confidence interval of 95% (mean difference ± 1.96 SDs).
Results: GFRs calculated using both alternative methods correlated strongly with those calculated using the gold standard. However, the correlation was stronger for the cystatin C method than for the β-trace protein method, and neither method produced reliably consistent GFRs.
Conclusion: This study demonstrated that cystatin C and β-trace protein do not reflect GFR with sufficient accuracy.
Keywords: beta trace protein; cystatin C; glomerular filtration rate.
© 2015 by the Society of Nuclear Medicine and Molecular Imaging, Inc.