Shuford Christopher M, McConnell Evan W, Dee Stacy, Grant Russell P
Laboratory Corporation of America Holdings, Center for Esoteric Testing, Burlington, NC, United States.
J Mass Spectrom Adv Clin Lab. 2023 Jan 24;28:1-8. doi: 10.1016/j.jmsacl.2023.01.003. eCollection 2023 Apr.
Determination of folate insufficiency is of considerable interest given its importance in fetal development and red blood cell formation; however, access to blood tests may be limited due to the requirement for phlebotomy as well as controlled temperature shipping of blood specimens to laboratories for testing due to the inherent instability of folate and its vitamers.
An LC-MS/MS test was developed and validated for the measurement of 5-methyltetrahydrofolate (5MTHF) in dried plasma specimens collected from fingerstick blood using a laminar flow blood separation device, as well as liquid venous plasma for comparison. Two pre-analytical factors investigated influencing the measurement of 5MTHF in dried plasma were hemolysis of the fingerstick blood during collection and storage/shipment of the dried plasma.
Although observed infrequently, hemolysis >10 % resulted in elevated 5MTHF measurements, but hemolysis >1 % resulted in elevated chloride measurements, which were necessary to normalize 5MTHF measurements for variation in volume of dried plasma specimens. Stability of 5MTHF was improved in dried plasma relative to liquid plasma at ambient temperatures, but not sufficiently to allow for uncontrolled temperature shipping despite controlling for humidity and light exposure. Shipping studies emulating ISTA procedure 7D were conducted with a reusable cold packaging solution. The packaging failed to stabilize 5MTHF in dried plasma specimens during a 2-day summer shipping evaluation, but did provide sufficient temperature control to stabilize 5MTHF during the overnight shipping evaluation.
Our studies provide boundary conditions with respect to hemolysis, storage, and shipping for successful analysis of 5MTHF from dried plasma specimens.
鉴于叶酸在胎儿发育和红细胞形成中的重要性，叶酸缺乏的测定备受关注；然而，由于需要进行静脉穿刺采血，以及叶酸及其维生素类似物本身不稳定，血液标本需要在受控温度下运送至实验室进行检测，因此进行血液检测可能会受到限制。
开发并验证了一种液相色谱 - 串联质谱法（LC-MS/MS），用于测量使用层流血液分离装置从指尖血采集的干燥血浆标本中的5-甲基四氢叶酸（5MTHF），同时也测量液体静脉血浆作为对照。研究了两个影响干燥血浆中5MTHF测量的分析前因素，即采集过程中指尖血的溶血以及干燥血浆的储存/运输。
虽然溶血情况不常出现，但溶血率>10%会导致5MTHF测量值升高，而溶血率>1%会导致氯化物测量值升高，这对于标准化干燥血浆标本体积变化后的5MTHF测量值是必要的。在环境温度下，干燥血浆中5MTHF的稳定性相对于液体血浆有所提高，但尽管控制了湿度和光照，仍不足以允许在不受控温度下运输。使用可重复使用的冷藏包装溶液进行了模拟ISTA程序7D的运输研究。在为期2天的夏季运输评估中，该包装未能稳定干燥血浆标本中的5MTHF，但在夜间运输评估中确实提供了足够的温度控制以稳定5MTHF。
我们的研究提供了关于溶血、储存和运输的边界条件，以便成功分析干燥血浆标本中的5MTHF。
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