The Stability of Analytes of Ionized Magnesium Concentration and Its Reference Range in Healthy Volunteers

Abstract

This study aimed to determine the stability of refrigerated analytes of iMg concentration at different time intervals and to establish iMg reference range in a cohort of healthy Omani volunteers (≥18 years). The concentrations of iMg were measured using the direct ion-selective electrode technique. Pearson’s and Lin’s concordance correlation coefficients along with the Bland–Altman plot were used to assess the levels of agreement between iMg concentrations of fresh and refrigerated blood samples at different time intervals. The study included 167 volunteers (51% females) with a median age of 21 (range: 20–25) years. The median, 2.5th, and 97.5th percentiles for fresh iMg reference ranges were 0.55, 0.47, and 0.68 mmol/L, respectively. The overall agreement between the fresh and refrigerated iMg concentrations was poor (rho-c = 0.51; p rho-c = 0.80), with a small average bias difference of 0.009 (95%CI; −0.025–0.043). A cut-off refrigeration period within ≤1 h at 2–8 °C can be considered an alternate time frame for the gold standard measurement (fresh or within 0.5 h).

Keywords

• reference range
• stability
• ionized magnesium
• whole blood
• direct ion selective electrode technique