BACKGROUND: The glycoprotein sclerostin (Scl; 22 kDa), which is involved in bone 
metabolism, may play a role in vascular calcification in haemodialysis (HD) 
patients. In the present study, we investigated the relation between serum Scl 
(sScl) and mortality. The effects of dialysis modality and the magnitude of the 
convection volume in haemodiafiltration (HDF) on sScl were also investigated.
METHODS: In a subset of patients from the CONTRAST study, a randomized 
controlled trial comparing HDF with HD, sScl was measured at baseline and at 
intervals of 6, 12, 24 and 36 months. Patients were divided into quartiles, 
according to their baseline sScl. The relation between time-varying sScl and 
mortality with a 4-year follow-up period was investigated using crude and 
adjusted Cox regression models. Linear mixed models were used for longitudinal 
measurements of sScl.
RESULTS: The mean (±standard deviation) age of 396 test subjects was 63.6 (±13.9 
years), 61.6% were male and the median follow-up was 2.9 years. Subjects with 
the highest sScl had a lower mortality risk than those with the lowest 
concentrations [adjusted hazard ratio 0.51 (95% confidence interval, CI, 
0.31-0.86, P = 0.01)]. Stratified models showed a stable sScl in patients 
treated with HD (Δ +2.9 pmol/L/year, 95% CI -0.5 to +6.3, P = 0.09) and a 
decreasing concentration in those treated with HDF (Δ -4.5 pmol/L/year, 95% CI 
-8.0 to -0.9, P = 0.02). The relative change in the latter group was related to 
the magnitude of the convection volume.
CONCLUSIONS: (i) A high sScl is associated with a lower mortality risk in 
patients with end-stage kidney disease; (ii) treatment with HDF causes sScl to 
fall; and (iii) the relative decline in patients treated with HDF is dependent 
on the magnitude of the convection volume.