Joëlle Schutten

Comparison of two methods for the assessment of intra-erythrocyte magnesium and its determinants 55 3 Characteristics Total (n=1669) Lipids metabolism Total cholesterol, mmol/L 5.01 ± 0.98 LDL cholesterol, mmol/L 3.26 ± 0.90 HDL cholesterol, mmol/L 1.49 ± 0.42 Triglycerides, mmol/L 1.07 (0.77-1.51) Blood pressure Systolic, mm Hg 127 ± 17 Diastolic, mm Hg 74 ± 9 Renal parameters Plasma creatinine, µmol/L 80.2 ± 16.9 Urinary creatinine excretion, mmol/24-h 13.3 ± 4.0 eGFR < 90 ml/min/1.73m2, % 32.2 Creatinine clearance, mL/min 116.5 ± 30.8 Plasma levels Sodium, mmol/L 140.9 ± 1.7 Potassium, mmol/L 4.01 ± 0.27 Hematology Hemoglobin, mmol/L 8.80 ± 0.79 Hematocrit, v/v 0.43 ± 0.03 MCV, fL 89.0 ± 4.14 Erythrocytes, 1012/L 4.79 ± 0.45 Leukocytes, 109/L 6.08 ± 1.61 Data are presented asmean ± SD,medianwith interquartile ranges (IQR) or percentages.Abbreviations: dIEM,direct intra-erythrocytemagnesium; iIEM,indirect intra-erythrocytemagnesium; eGFR,estimated glomerular filtration rate; HbA1c, hemoglobin A1c, MCV, mean corpuscular volume. aAvailable in 1161 subjects; bAvailable in 1153 subjects. Method comparison We compared dIEM and iIEM in 1669 samples from the LifeLines study, both expressed as mmol per liter packed blood cells and mmol per 1012 red blood cells. Mean dIEM concentrations were 1.73 ± 0.24 mmol/L and 0.20 ± 0.04 mmol/1012 cells and mean iIEM concentrations were 2.11 ± 0.24 mmol/L and 0.25 ± 0.04 mmol/1012 cells. When expressed in magnesium per liter packed blood cell, we found a Pearson correlation coefficient of 0.57 between dIEM and iIEM. Ordinary linear regression analysis produced an intercept of 1.092 (1.019; 1.164) and a slope of 0.590 (95% CI: 0.549; 0.631) and Passing-Bablok regression produced an intercept of 0.263 (95% CI: -0.156; 0.359) and Table 1. (Continued)

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