Vitamin K status and vascular calcification biomarkers as determinants of carotid plaque in peritoneal dialysis: a prospective study.

BACKGROUND: Vitamin K deficiency impairs the activation of calcification inhibitors such as matrix Gla protein, promoting vascular calcification in CKD. Protein induced by vitamin K absence-II (PIVKA-II) is a filtration-independent marker of vitamin K status validated in hemodialysis, yet no data exist in peritoneal dialysis (PD).

METHODS: Sixty prevalent PD patients at a single tertiary center were prospectively followed for 1 year. Serum PIVKA-II, dephosphorylated uncarboxylated matrix Gla protein (dp-ucMGP), and bone morphogenetic protein-2 (BMP-2) were measured at baseline and 12 months. Carotid plaque was assessed by ultrasonography. Independent predictors of plaque were identified by multivariable logistic regression and ROC analysis.

RESULTS: Carotid plaque was present in 36 patients (60%). Vitamin K deficiency (PIVKA-II >40 mAU/mL) was identified in 43.3% and was more prevalent in plaque-positive patients (55.5% vs 25.0%; p = 0.019). All three biomarkers were significantly elevated in the plaque group. Age (OR 1.26; 95% CI 1.07-1.42; p = 0.004) and PIVKA-II (OR 1.71; 95% CI 1.09-2.70; p = 0.022) independently predicted plaque. The area under the ROC curve was 0.766 (p = 0.001) with an optimal cutoff of 35.09 mAU/mL (sensitivity 86.1%, specificity 50.0%). Over 12 months, plaque prevalence rose to 70%; baseline BMP-2 was the sole predictor of new plaque development (p = 0.022).

CONCLUSION: PIVKA-II-assessed vitamin K deficiency is common in PD and independently associated with carotid plaque. A threshold of 35 mAU/mL may be more sensitive than the conventional 40 mAU/mL cutoff, supporting PIVKA-II screening and targeted supplementation trials in PD.