Agreement Between Cystatin-C and Creatinine Based EGFR Estimates After a 12-month Exercise Intervention in Patients with Chronic Kidney Disease

Background: Estimation of GFR (eGFR) using formulae based on serum creatinine concentrations are commonly used to assess kidney function. Physical exercise can increase creatinine turnover and lean mass; therefore, this method may not be suitable for use in exercising individuals. Cystatin-C based eGFR formulae may be a more accurate measure of kidney function when examining the impact of exercise on kidney function. The aim of this study was to assess the agreement of four creatinine and cystatin-C based estimates of GFR before and after a 12-month exercise intervention.

Methods: One hundred forty-two participants with stage 3-4 chronic kidney disease (CKD) (eGFR 25-60 mL/min/1.73 m) were included. Subjects were randomised to either a Control group (standard nephrological care [n = 68]) or a Lifestyle Intervention group (12 months of primarily aerobic based exercise training [n = 74]). Four eGFR formulae were compared at baseline and after 12 months: 1) MDRDcr, 2) CKD-EPIcr, 3) CKD-EPIcys and 4) CKD-EPIcr-cys.

Results: Control participants were aged 63.5[9.4] years, 60.3% were male, 42.2% had diabetes, and had an eGFR of 40.5 ± 8.9 ml/min/1.73m. Lifestyle Intervention participants were aged 60.5[14.2] years, 59.5% were male, 43.8% had diabetes, and had an eGFR of 38.9 ± 8.5 ml/min/1.73m. There were no significant baseline differences between the two groups. Lean mass (r = 0.319, p < 0.01) and grip strength (r = 0.391, p < 0.001) were associated with serum creatinine at baseline. However, there were no significant correlations between cystatin-C and the same measures. The Lifestyle Intervention resulted in significant improvements in exercise capacity (+ 1.9 ± 1.8 METs, p < 0.001). There were no changes in lean mass in both Control and Lifestyle Intervention groups during the 12 months. CKD-EPIcys was considerably lower in both groups at both baseline and 12 months than CKD-EPIcr (Control = - 10.5 ± 9.1 and - 13.1 ± 11.8, and Lifestyle Intervention = - 7.9 ± 8.6 and - 8.4 ± 12.3 ml/min/1.73 m), CKD-EPIcr-cys (Control = - 3.6 ± 3.7 and - 4.5 ± 4.5, and Lifestyle Intervention = - 3.6 ± 3.7 and - 2.5 ± 5.5 ml/min/1.73 m) and MDRDcr (Control = - 9.3 ± 8.4 and - 12.0 ± 10.7, Lifestyle Intervention = - 6.4 ± 8.4 and - 6.9 ± 11.2 ml/min/1.73 m).

Conclusions: In CKD patients participating in a primarily aerobic based exercise training, without improvements in lean mass, cystatin-C and creatinine based eGFR provided similar estimates of kidney function at both baseline and after 12 months of exercise training.

Trial Registration: The trial was registered at www.anzctr.org.au (Registration Number ANZCTR12608000337370) on the 17/07/2008 (retrospectively registered).