Variability within individuals of plasma ionic magnesium concentrations

✍ Scribed by Ian J Newhouse; Kris P Johnson; William J Montelpare; Jim E McAuliffe

• Publisher: BioMed Central
• Year: 2002
• Tongue: English
• Weight: 227 KB
• Volume: 2
• Category: Article
• ISSN: 1472-6793
• DOI: 10.1186/1472-6793-2-6

✦ Synopsis

Background: With the invention of the ion-selective electrode (ISE), ionic magnesium (iMg) is a common blood assay. This could be advantageous, as iMg is the biologically active form of Mg. There is some evidence that iMg has considerable within subject variability.

Results: Individual ranges averaged .08 mmol/L (range .05 to .14). Coefficients of variation (CV) ranged from 3% to 7% (mean 4%) while analytical variation was determined to be 2.3%. Biological variability thus accounts for almost half of the variability, which is clinically significant, as 9 of the 13 subjects recorded at least one value below a reference range of .46 -.60 mmol/L. A significant within-day variation (p < .001) was noted, with differences between 7:00 and 10:00 as well as 10:00 and 22:00. Between day variations were not significant (p = .56).

Conclusions: A plausible explanation of this data is that iMg has a circadian rhythm. Thus, cautious interpretation of single iMg values is warranted until future research determines the nature of iMg variability.