Background. Indoxyl sulphate (IS) and p-cresyl sulphate (PCS) are uraemic toxins that have similar protein binding, dialytic clearance and proinflammatory features. However, only a few prospective studies have evaluated possible associations between these two retained solutes and renal disease progression in chronic kidney disease (CKD) patients.Methods. This prospective observational study evaluated independent associations between serum total IS and PCS with renal progression in a selected cohort of patients having different stages of CKD. Baseline PCS and IS were correlated with renal progression [defined as decrements in estimated glomerular filtration rate (eGFR) > 50% from baseline or progression to end-stage renal disease (ESRD)] and death during a follow-up period of 24 months.Results. Of 268 patients, 35 (13.1%) had renal progression and 14 (5.2%) died after a mean follow-up of 21 ± 3 months. Univariate Cox regression analysis followed by multivariate analysis showed that high-serum PCS levels were associated with renal progression and all-cause mortality independent of age, gender, diabetes status, albumin levels, serum IS, serum creatinine, Ca × P product, intact parathyroid hormone, haemoglobin or high-sensitivity C-reactive protein level. Serum IS was only associated with renal progression; however, the predictive power of serum IS was weakened when serum PCS was also present in the analytical model.Conclusions. In addition to traditional and uraemia-related risk factors such as renal function, serum IS and PCS levels may help in predicting the risk of renal progression in patients having different stages of CKD.

Our randomized study suggests that a standardized SMS program may play a significant role in reducing CKD progression and morbidity of late-stage CKD patients.

MPE based on the NKF/DOQI guidelines may decrease the incidence of dialysis and reduce mortality in late-stage CKD patients.

Serum free PCS levels may help in predicting risk of all-cause and CV mortality in elderly HD patients beyond traditional and uremia related risk factors.