The Effect of On-Line Hemodiafiltration, Vegetarian Diet, and Urine Volume on Advanced Glycosylation End Products Measured by Changes in Skin Auto-Fluorescence

Increasing urea clearance by hemodialysis (HD) has not improved patient survival. Hemodiafiltration (HDF) has been reported to reduce cardiovascular mortality. HDF increases middle sized solute clearances. Advanced glycosylation end products (AGEs) are associated with increased cardiovascular mortality. We wished to determine whether HDF reduces AGEs. Skin auto-fluorescence (SAF) measures circulating AGEs deposited in the skin. We compared SAF measurements 12 months apart in high flux HD and HDF patients. At enrollment SAF was not different (HD 3.34 +/- 0.71 vs. HDF 3.48 +/- 1.05 AU). At seven months after completion of SAF measurement, one hemodiafiltration center returned to hemodialysis, and one hemodialysis center converted to hemodiafiltration. In the 66 patients treated solely by high flux HD, SAF increased (3.36 +/- 0.71 to 3.82 +/- 0.88 AU, P < 0.001), whereas there was no change for 47 exclusively treated by HDF (3.45 +/- 1.13 to 3.44 +/- 0.85 AU, P > 0.9). SAF increased in 34 patients switching from HDF to high flux HD (3.52 +/- 0.94 vs. 3.88 +/- 1.05, P < 0.05), with no significant change for 33 patients converting from high flux HD to HDF (3.32 +/- 0.72 to 3.48 +/- 1.07 AU, P > 0.3). On multivariate analysis, SAF was associated with older age (beta coefficient 0.013, P = 0.002), prescription of insulin (beta 0.29, P = 0.016), lanthanum (beta 0.36, P = 0.004), and warfarin (beta 0.62, P = 0.012), whereas vegetarian diet and > 250 mL/day residual urine volume were negatively associated with SAF (beta -0.58, P = 0.002 and beta -0.26, P = 0.033 respectively). Residual urine output and vegetarian diet were associated with lower AGE deposition. Whereas SAF increased over time in patients treated with high flux HD, there was no statistical change in SAF in those exclusively treated by HDF.