Agreement between cystatin-C and creatinine based eGFR estimates after a 12-month exercise intervention in patients...

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.

One hundred forty-two participants with stage 3-4 chronic kidney disease (CKD) (eGFR 25-60 mL/min/1.73 m²) 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.

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/1.73m². 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/1.73m². 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 m²), 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 m²) 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 m²).

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.

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