Rapid assessment of renal reserve in young adults by cystatin C

Abstract

Background. The kidney can increase glomerular filtration rate (GFR) in response to a protein load (renal reserve). In a pilot study of healthy young adults we examined renal reserve using changes in serum cystatin C (cysC). Methods. Glomerular filtration rate was obtained using iohexol single slope plasma disappearance. To stimulate GFR, subjects ingested a beefburger containing 60 grams of protein. CysC was measured by immunonephelometry before and 125–141 minutes after protein loading. Results. All subjects were found to have a normal iohexol plasma disappearance GFR with a mean of 104.6 ± 9.9 mL/min per 1.73 m². CysC decreased in each subject after the meat meal. Baseline cysC-based estimated GFR was 98.1 ± 9.1 mL/min per 1.73 m² with a mean increase of 12.0 ± 5.2 (p = 0.0003). Conclusions. Our study showed a consistent decrease in serum cysC and increase in cysC-based estimated GFR following a protein load in young adults. Further studies are needed using renal clearance methods to confirm that cysC accurately determines renal reserve in patients with and without chronic kidney disease.

Key Words::

• Chronic kidney disease
• clearance
• creatinine
• cystatin C
• estimated GFR
• glomerular filtration rate

Acknowledgements

We are grateful to GE Healthcare, Amersham Division, for providing the iohexol (Omnipaque™ 300 for the baseline GFR measurements. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Declaration of interest: The authors report no conflict of interest. The authors alone are responsible for the content and writing of the article.

This study was supported in part by a grant from the National Kidney Foundation (D.Y.F.) as well as from the National Institutes of Health T32 Training Grant (T32HD057821). The project described in this publication was also supported by the University of Rochester CTSA award numbers UL1 RR024160 and UL1 TR000042 from the National Center for Research Resources and the National Center for Advancing Translational Sciences of the National Institutes of Health.