Greenway D C, Hindmarsh J T, Wang J, Khodadeen J A, Hébert P C
Department of Pathology, Ottawa General Hospital, Ontario, Canada.
Clin Biochem. 1996 Dec;29(6):515-20. doi: 10.1016/s0009-9120(96)00091-4.
To establish a reference interval for ionized magnesium (iMg), to evaluate the stability of whole blood iMg under varied laboratory storage conditions, and to study the correlation between total and iMg in healthy volunteers and in an intensive care unit (ICU) population.
Blood specimens were collected anaerobically from 125 healthy volunteers and 200 ICU patients into tubes containing lithium heparin, transported to the laboratory on ice, stored at 4 degrees C and analyzed within 2 h on a NOVA 8 Electrolyte Analyzer. Additional specimens were stored under different conditions before analysis to assess the stability of iMg.
In healthy volunteers, the mean whole blood iMg level was 0.52 mmol/L with a range of 0.44 to 0.59 mmol/L. The iMg/total serum Mg ratio was at 0.60 (0.50-0.69). Regression analysis of iMg vs total Mg produced a correlation coefficient (r) of 0.48 (p < 0.0001). Ionized Mg levels were comparable between males and females (0.52 +/- 0.04 vs 0.51 +/- 0.03, p = 0.38). In the ICU group, a wider range of iMg results was observed (0.35-0.78 mmol/L) and the correlation between iMg and total Mg was r = 0.71 (p < 0.0001). Storage of whole blood specimens in uncapped tubes at room temperature resulted in a small, but significant, decrease in iMg over a 6-h period. Little change was seen in capped tubes stored either at room temperature or at 4 degrees C. over 6 h, or at 4 degrees C. over 5 days.
Using the NOVA 8 Electrolyte Analyzer, we established a reference interval for whole blood iMg in a healthy Canadian population. The correlation between ionized Mg and total Mg was weak, but statistically significant. Ionized Mg levels in lithium heparin tubes were stable over 5 days when specimens were stored at 4 degrees C, suggesting that specimens may be stored at least overnight prior to processing.
建立游离镁（iMg）的参考区间，评估全血iMg在不同实验室储存条件下的稳定性，并研究健康志愿者和重症监护病房（ICU）人群中总镁和iMg之间的相关性。
从125名健康志愿者和200名ICU患者中厌氧采集血液标本，放入含有肝素锂的试管中，在冰上运至实验室，于4℃储存，并在2小时内用NOVA 8电解质分析仪进行分析。在分析前，将额外的标本储存在不同条件下，以评估iMg的稳定性。
在健康志愿者中，全血iMg的平均水平为0.52 mmol/L，范围为0.44至0.59 mmol/L。iMg/血清总镁比值为0.60（0.50 - 0.69）。iMg与总镁的回归分析得出相关系数（r）为0.48（p < 0.0001）。男性和女性的游离镁水平相当（0.52±0.04对0.51±0.03，p = 0.38）。在ICU组中，观察到iMg结果的范围更广（0.35 - 0.78 mmol/L），iMg与总镁之间的相关性为r = 0.71（p < 0.0001）。将全血标本储存在室温下的无盖试管中，在6小时内iMg会有小幅但显著的下降。在室温或4℃下储存6小时，或在4℃下储存5天的有盖试管中，变化很小。
使用NOVA 8电解质分析仪，我们建立了加拿大健康人群全血iMg的参考区间。游离镁与总镁之间的相关性较弱，但具有统计学意义。当标本在4℃储存时，肝素锂试管中的游离镁水平在5天内保持稳定，这表明标本在处理前至少可以储存过夜。
