IFCC guideline for sampling, measuring and reporting ionized magnesium in plasma.
Analyzers with ion-selective electrodes (ISEs) for ionized magnesium (iMg) should yield comparable and unbiased results for iMg. This IFCC guideline on sampling, measuring and reporting iMg in plasma provides a prerequisite to achieve this goal [in this document, "plasma" refers to circulating plasma and the forms in which it is sampled, namely the plasma phase of anticoagulated whole blood (or "blood"), plasma separated from blood cells, or serum]. The guideline recommends measuring and reporting ionized magnesium as a substance concentration relative to the substance concentration of magnesium in primary aqueous calibrants with magnesium, sodium, and calcium chloride of physiological ionic strength. The recommended name is "the concentration of ionized magnesium in plasma". Based on this guideline, results will be approximately 3% higher than the true substance concentration and 4% lower than the true molality in plasma. Calcium ions interfere with all current magnesium ion-selective electrodes (Mg-ISEs), and thus it is necessary to determine both ions simultaneously in each sample and correct the result for Ca2+ interference. Binding of Mg in plasma is pH-dependent. Therefore, pH should be measured simultaneously with iMg to allow adjustment of the result to pH 7.4. The concentration of iMg in plasma may be physiologically and clinically more relevant than the concentration of total magnesium. Furthermore, blood-gas analyzers or instruments for point-of-care testing are able to measure plasma iMg using whole blood (with intact blood cells) as the sample, minimizing turn-around time compared to serum and plasma, which require removal of blood cells.
Department of Chemistry, University of Newcastle upon Tyne, UK.
Mohammed C
MC
Ben Rayana
Robert W
RW
Burnett
Arthur K
AK
Covington
Paul
P
D'Orazio
Niels
N
Fogh-Andersen
Ellis
E
Jacobs
Wolf R
WR
Külpmann
Katsuhiko
K
Kuwa
Lasse
L
Larsson
Andrzej
A
Lewenstam
Anton H J
AH
Maas
Gerhard
G
Mager
Jerzy W
JW
Naskalski
Anthony O
AO
Okorodudu
Christoph
C
Ritter
Andrew
A
St John
D001774:Blood Chemical Analysis / Q000295:instrumentation / Q000379:methods; D001784:Blood Gas Analysis / Q000295:instrumentation / Q000379:methods; D002118:Calcium / Q000097:blood; D002138:Calibration; D004573:Electrolytes; D004912:Erythrocytes / Q000737:chemistry; D017408:Guidelines as Topic; D006801:Humans; D006863:Hydrogen-Ion Concentration; D017736:Ion-Selective Electrodes; D008274:Magnesium / Q000097:blood*; D019095:Point-of-Care Systems; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012964:Sodium / Q000097:blood
D004573:Electrolytes; D012964:Sodium; D008274:Magnesium; D002118:Calcium