Baek E J, Park I K
Department of Laboratory Medicine, Hanyang University College of Medicine, Seoul, Korea.
Scand J Clin Lab Invest. 2005;65(2):107-10. doi: 10.1080/00365510510013460.
The aim of this study was to evaluate whether reporting serum level of ionized magnesium (iMg) is appropriate when affected by various conditions such as exposure to air and delayed measurement. Serum levels of pH, iMg and normalized magnesium (nMg, normalized or adjusted concentration of iMg to pH 7.40) from 28 inpatients were measured at intervals of 3 min after exposing the samples to air at room temperature. Serum from 30 inpatients was stored in closed tubes at 4 degrees C and -20 degrees C and iMg and nMg levels were measured after 2 days. It was found that serum iMg and nMg concentrations exposed to air were decreased by 0.0023 mmol/l and 0.0001 mmol/l per minute, respectively. nMg did not display any significant changes compared with iMg at 0 min, whereas iMg showed significant changes, which exceeded between-day precision. For the stored serum, only iMg of serum at -20 degrees C showed no statistically significant changes (p = 0.169). It is concluded that to report the result as iMg, the sample should be kept anaerobically, and if exposed to air, the result should be reported as nMg. For storage, iMg of serum kept anaerobically at -20 degrees C is reliable.
本研究的目的是评估在受到诸如暴露于空气和延迟测量等各种条件影响时，报告血清离子镁（iMg）水平是否合适。在室温下将28例住院患者的样本暴露于空气后，每隔3分钟测量其血清pH值、iMg和标准化镁（nMg，iMg在pH 7.40时的标准化或校正浓度）水平。将30例住院患者的血清保存在封闭管中，分别置于4℃和-20℃，2天后测量iMg和nMg水平。结果发现，暴露于空气的血清iMg和nMg浓度分别以每分钟0.0023 mmol/L和0.0001 mmol/L的速度下降。与0分钟时的iMg相比，nMg没有显示出任何显著变化，而iMg显示出显著变化，超过了日间精密度。对于储存的血清，只有-20℃血清的iMg没有显示出统计学上的显著变化（p = 0.169）。结论是，若要报告iMg结果，样本应保持厌氧状态，如果暴露于空气，结果应报告为nMg。对于储存，-20℃厌氧保存的血清iMg是可靠的。
