(P11-024-23) Measurement of Ionized Magnesium in Fresh Whole Blood Versus Frozen Serum Samples

Objectives: The US population under-consumes magnesium, an essential macro-mineral, thus there is a need for broad screening for magnesium deficiency within this population. Ionized magnesium (iMg) in whole blood can be quickly and simply measured using ion selective electrodes. To determine whether fractionation to serum and then freezing/storing impacts the measure of iMg, we compared iMg measures obtained from fresh whole blood samples to the same samples in the form of frozen serum.

Methods: This study analyzed serum samples from bioavailability study of a single-dose 300mg magnesium chloride supplement (Zhan et al., Nutrients, 2020).  Samples from 6 participants were collected at nine timepoints (i.e., 0, 0.5, 1, 2, 3, 4, 6, 8, 24 hours) and analyzed for iMg post supplement administration. Blood was then rapidly processed to serum and frozen at -80°C.  iMg was obtained using the Nova 8 electroanalyzer instrument (Nova Biomedical Waltham, MA, USA).  A linear mixed model was conducted with iMg as a dependent variable and both group (i.e., fresh versus frozen) and timepoint as categorical measures.  Significance was set at P < 0.05.

Results: In readings obtained from both fresh whole blood and frozen serum samples, iMg concentrations increased over 24 hours following administration of the Mg supplement (P < 0.001).  There was no difference between the iMg values obtained from fresh whole blood versus frozen serum samples, and there was no interaction between timepoint and group (P = 0.569 and 0.366, respectively). 

Conclusions: Serum samples that are fractionated quickly and frozen may be used in studies measuring iMg, since freezing and storing serum did not impact the iMg measures obtained from fresh whole blood.  Our findings provide an opportunity to measure iMg in archived serum samples, which may help broaden screening for magnesium deficiency in populations studies.  

Funding Sources: Nova Biomedical and New Capstone Inc., provided equipment and supplies.