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Abstract: FR-PO691

Use of Raman Spectroscopy Analysis to Evaluate the Molecular Composition of Spent Peritoneal Dialysate and Urine over Time

Session Information

Category: Dialysis

  • 703 Dialysis: Peritoneal Dialysis

Authors

  • Pirkle, James L., Wake Forest School of Medicine, Winston Salem, North Carolina, United States
  • Robertson, John L., Virginia Tech, Blacksburg, Virginia, United States
Background

Common indices to assess peritoneal dialysis (PD) adequacy – Kt/V urea and creatinine clearance – may not reflect clearance of other small and middle-molecular weight molecules that may be more important in the pathogenesis of uremia and patient outcomes. These indices may not reflect changes in residual renal function, peritoneal membrane integrity, local/systemic inflammation, patient metabolism, or mineral/electrolyte balance. Identification of other potentially important molecules in both spent dialysate (SD) and urine (UR) may provide better measures of treatment adequacy. However, analysis of these potentially-important molecules, with current technology (chromatography, mass spectroscopy), is time-consuming, expensive, and unlikely to be widely available in clinical settings.

Methods

We used novel methods, based on Raman spectroscopy and computational analysis, to study the molecular composition of SD and UR collected periodically from 15 PD patients over a two-year period of observation. Raman spectra were generated by irradiation of SD and UR samples at 785 nm, corrected for incident (background) radiation and then computationally normalized. The spectra of SD and UR samples from PD patients were compared to analytical standards, to unused dialysate fluid (SD samples) and urine (UR) collected from consented, healthy volunteers. Quantification of prominent spectral peaks (urea, creatinine, glucose, for example) was achieved by comparison with analytical standard calibration curves.

Results

As expected, spectra of SD and UR differed significantly. Of note, SD spectra among 15 patients also differed significantly from one another, as did UR spectra. For individual patients, both SD and UR spectra varied over time, reflecting changes in types of molecules being dialyzed and/or excreted in urine. Variations in either SD or UR spectra were not well-correlated to Kt/V urea or creatinine clearance. Prominent spectral peaks representing collagen and nucleic acids in some SD specimens may signal changes in peritoneal membrane integrity; this requires further analysis.

Conclusion

Changes in the molecular composition of peritoneal dialysate and urine over time can be identified using computational Raman spectroscopy. This method may yield a viable tool for assessing the clinical effectiveness of the peritoneal dialysis therapy.