Patients with advanced chronic kidney disease and vascular calcification have a large hydrodynamic radius of secondary calciprotein particles.

BACKGROUND: The size of secondary calciprotein particles (CPP2) and the speed of transformation (T50) from primary calciprotein particles (CPP1) to CPP2 in serum may be associated with vascular calcification (VC) in patients with chronic kidney disease (CKD). METHODS: We developed a high throughput, microplate-based assay using dynamic light scattering (DLS) to measure the transformation of CPP1 to CPP2, hydrodynamic radius (Rh) of CPP1 and CPP2, T50 and aggregation of CPP2. We used this DLS assay to test the hypothesis that a large Rh of CPP2 and/or a fast T50 are associated with VC in 45 participants with CKD Stages 4-5 (22 without VC and 23 with VC) and 17 healthy volunteers (HV). VC was defined as a Kauppila score >6 or an Adragao score ≥3. RESULTS: CKD participants with VC had larger cumulants Rh of CPP2 {370 nm [interquartile range (IQR) 272-566]} compared with CKD participants without VC [212 nm (IQR 169-315)] and compared with HV [168 nm (IQR 145-352), P < 0.01 for each]. More CPP2 were in aggregates in CKD participants with VC than those without VC (70% versus 36%). The odds of having VC increased by 9% with every 10 nm increase in the Rh of CPP2, after adjusting for age, diabetes, serum calcium and phosphate [odds ratio 1.09, 95% confidence interval (CI) 1.03, 1.16, P = 0.005]. The area under the receiver operating characteristic curve for VC of CPP2 size was 0.75 (95% CI 0.60, 0.90). T50 was similar in CKD participants with and without VC, although both groups had a lower T50 than HV. CONCLUSIONS: Rh of CPP2, but not T50, is independently associated with VC in patients with CKD Stages 4-5.