P0699EVALUATION OF CALCIUM/MAGNESIUM RATE AND OTHER PREDICTORS OF CARDIOVASCULAR MORTALITY IN CHRONIC KIDNEY DISEASE
Authors: Carias Eduarda , Mendes Filipa , Fragoso André , Leão Neves Pedro , Silva Ana 
Published: June 2020

Abstract

Background and Aims
Cardiovascular disease (CVD) is the main cause of death in chronic kidney patient. The interaction between calcium and magnesium and mineral metabolism have been identified as risk markers for CVD.
The main objective was to identify the variables associated with cardiovascular and other causes of mortality in a group of patients with stage 4 of chronic kidney disease (CKD).

Method
This was a prospective analysis conducted in an outpatient nephropathy clinic between 2005-2018, enrolling 692 patients with stage 4 CKD. Based on the calcium/magnesium ratio (rCaMg) the subjects were divided into 4 risk groups according to the following criteria: &lt;25th percentile (rCaMg &lt; 3.8mg/dl; n=168) – G1; 25-50th percentile (rCaMg: 3.8-4.7; n=171) – G2; 50-75th percentile (rCaMg: 4.7-8.6; n=188) – G3; and &gt;75th percentile (rCaMg: &gt; 8.6; n=165) - G4.
Descriptive statistics, ANOVA, chi-square and Log Rank test were used for comparison between groups. Bonferroni test was used as a post-hoc test. Kaplan-Meier analysis was used to evaluate mortality. The Kaplan-Meier method for measuring patient survival rate was applied and a comparison between the four percentiles was based on the log rank test
The multinomial regression models were used to assess predictive factors for cardiovascular mortality. CHAID analysis was used to assign patients to risk groups.

Results
The mean age was 70 years, 53.5% women, with an eGFR of 19.9 ml/min (sd 8.1).
Differences among groups were evaluated with the use of an analysis of variance (ANOVA) model. Age (p&lt;0.001), hemoglobin (p&lt;0.001), phosphorous (p&lt;0.001), pulse pressure (p&lt;0.001), parathormone (p&lt;0.001), estimated glomerular filtration rate (p&lt;0.001) showed significant differences between groups. A post HOC analysis showed that G4 (rCaMg: &gt; 8.6) were older (p&lt;0.001), had lower hemoglobin levels (p&lt;0.001), increased pulse pressure (p&lt;0.001), higher phosphorus (p&lt;0.001) and parathormone levels (p&lt;0.001) and lower eGFR (p&lt;0.001), than groups 1 and 2.
Survival at 84 months was progressively shorter with higher rCaMg (G- 1=81.4%, G-2:70.7, G- 3=60.5%, G- 4=28.4%. log Rank =xxx, p=0.004)
Multinomial regression analysis showed that Phosphorus; ORa: 1.946 (CI 1.194-3.169), p=0.007, rCaMg; ORa: 1.106 (CI 1.071-1.261) p=0.031, Age: ORa; 1.032 (CI 1.007-1.058) p=0.013, Pulse pressure: ORa; 1.033 (CI 1.007-1.060) p=0.011 were linked to increased cardiovascular mortality.
CHAID analysis identified that in 43.7% of patients with P&gt; 4.1 mg/dl, 15.5% were associated with cardiovascular mortality (p&lt;0.001), the model correctly classified 84.1% of patients and the estimate of the risk misclassification of events was 0.159±0.014.

Conclusion
The calcium/magnesium ratio was shown to be a strong predictor of cardiovascular mortality in patients with stage 4 chronic kidney disease.
After CHAID analysis the phosphorus level was assumed to be strongest predictor of cardiovascular mortality in this group of patients.