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Kidney Week

Abstract: PO0790

The Usefulness of Calcium/Magnesium Ratio in the Risk Stratification of Early Onset of Renal Replacement Therapy

Session Information

Category: Dialysis

  • 701 Dialysis: Hemodialysis and Frequent Dialysis


  • Afonso, Rita Serra, Centro Hospitalar do Algarve EPE, Faro, Faro, Portugal
  • Cabrita, Ana, Centro Hospitalar do Algarve EPE, Faro, Faro, Portugal
  • Silva, Ana Paula, Centro Hospitalar do Algarve EPE, Faro, Faro, Portugal

Recently, a growing number of studies have reported a close relationship between high serum calcium (Ca) and low serum magnesium (Mg) with vascular calcification. Endothelial dysfunction and vascular inflammation seem plausible risk factors for enhanced progression of kidney disease. The aim of this study is to evaluate the role of calcium/magnesium ratio as risk factor in CKD progression.


Observational, prospective study involving 693 patients (female=371) with stage 4/5 CKD. Patients were divided into two groups, according to the development of ESRD: G1 (n=541), who did not start renal replacement therapy (RRT) and G2 (n=152), who had started RRT. Several laboratory parameters were measured. Baseline characteristics were recorded and compared. Multivariate Cox regression analysis was used to identify independent factors associated with RRT initiation. A modified Poisson regression with robust error variance was used to estimate the cumulative relative risk for RRT initiation.


The mean age was 70.09±12.51 years and eGFR was 19.91±8.11 mL/min. G2 had significantly lower serum levels of Hb (11.75vs10.95 g/dl,p= 0.000), Ca (9.34vs8.95 mg/dl,p=0.000), Mg (1.92vs1.40 mg/dl,p= 0.0001), albumin (4.00vs3.88 g/dl,p= 0.03) and cholesterol (183.17vs172.39 mg/dl,p=0.01), and higher serum levels of phosphorus (3.88vs4.69 mg/dl,p=0.0001), Ca/Mg ratio (5.73vs7.56,p= 0.0001) and PTH (209.71vs338.84 pg/ml,p= 0.0001). In univariate Cox regression analysis, age, Hb, eGFR, Ca, Mg, phosphorus, Ca/Mg ratio and PTH correlated with onset of RRT, which were further tested using a multivariate COX regression. The results showed a relationship between high levels of phosphorus (HRa=1.638,p=0.001) and Ca/Mg ratio (HRa=1.292;p=0.002), and low levels of Mg (HRa=0.761,p=0.005) and eGFR (HRa=0.934;p=0.0001) were independent risk factors to start RRT. Poisson regression showed that high Ca/Mg ratios (aPR=1.986; 95% CI 1.026-3.051;p=0.002), high phosphorus levels (aPR=1.607;95% CI 1.324-1.950;p<0.0001) and low levels eGFR (aPR=0.927; 95% CI 0.891-0.964;p<0.0001) were associated with a cumulative risk for initiation of RRT.


Our results suggest that the calcium/magnesium ratio is an independent predictive factor for the initiation of RRT. Further studies are required to validate the use of this novel marker as predictor of CKD progression.