Well-Being, Protein-Bound Toxins, and Dietary Fibre in Patients with Kidney Disease: Have We Been Missing the Obvious?

AIM: To explore the associations between protein-bound uraemic toxins (PBTs), fibre intake and patient-focused outcomes in patients on kidney replacement therapy. BACKGROUND: Despite removal of small water-soluble uraemic toxins, dialysis patients continue to experience high morbidity and mortality. Recent evidence suggests strong associations between PBTs and poorer patient outcomes and symptom burden. Reducing the generation of PBTs by increasing dietary fibre may be an alternate approach to better patient outcomes. METHOD: This was a cross-sectional study of haemodialysis (HD), peritoneal dialysis (PD) and kidney transplant patients to determine the associations between uraemic toxins [p-cresyl sulfate (PCS) and indoxyl sulfate (IS)], fibre intake and patient-focused outcomes, incorporating the Integrated Palliative Outcome Scale-Renal (IPOS-renal) and EQ-5D-5L to determine symptom burden and quality of life, while physical capacity was determined using the timed up and go(TUG) test and handgrip strength (HGS). RESULTS: Ninety participants completed the study (n = 30 in each group). There was a correlation between PBTs and the IPOS-renal score, where higher toxin levels were associated with a higher symptom burden. This was the strongest for PCS, where the significance remained after accounting for age and co-morbidities (p < 0.05). Higher PBT levels were also associated with lower HGS (p < 0.05). There was a negative correlation between fibre intake and PBTs, serum PCS (r = -0.36, p < 0.05) and serum IS (r = -0.27, p < 0.05). Lower fibre intake was also associated with a higher symptom burden measured by the IPOS-renal (p < 0.05). Transplant patients consistently performed better, with a reduced symptom burden and improved physical ability compared to dialysis patients. CONCLUSION: PBTs were associated with symptom burden, and lower physical ability was associated with both PBTs and patient-focused outcomes, and this needs to be further investigated in larger studies.