We analyzed four GFR estimating equations in participants of the Angiotensin II Blockade for Chronic Allograft Nephropathy Trial ( NCT 00067990 ) : Chronic Kidney Disease Epidemiology Collaboration equations based on serum cystatin C and creatinine ( eGFR ( CKD-EPI-Creat + CysC ) ) , cystatin C alone ( eGFR ( CKD-EPI-CysC ) ) , creatinine alone ( eGFR ( CKD-EPI-Creat ) ) and the Modification of Diet in Renal Disease study equation ( eGFR ( MDRD ) ) .