IDM Service, Institute of Liver Studies, King's College Hospital, London, United Kingdom.
Ther Drug Monit. 2012 Apr;34(2):148-52. doi: 10.1097/FTD.0b013e31824c2d50.
The immunosuppressant mycophenolic acid (MPA) is widely used in solid organ transplantation and increasingly in hematological conditions and autoimmune disease. Concentration monitoring is generally restricted to specialist laboratories associated with transplant centers to which samples are referred, and delays in transit may occur both from the patient to the local laboratory and from there to the specialist laboratory. The instability of the mycophenolate glucuronides in plasma is well described, but the data on MPA stability in patient samples are limited, particularly in whole blood. This study was designed to assess the stability of MPA in patient samples and to establish the correct sample type and optimal transport conditions for therapeutic drug monitoring.
Whole-blood samples received in the laboratory for MPA estimation within 2 hours of phlebotomy were aliquoted, separated, and stored at a range of temperatures designed to mimic the range of transit times and conditions seen in this laboratory. Ten whole-blood samples were stored for a maximum of 4 weeks at 4°C, 21°C, or 35°C and plasma at -20°C, 4°C, 21°C, and 35°C. MPA concentrations were measured by liquid chromatography-tandem mass spectrometry.
In whole blood at 35°C, there was a significant increase (P = 0.004) in median MPA concentration over time, but concentrations decreased in some samples. At 21°C and 4°C, there were more modest increases (P = 0.04 and 0.02). In plasma at 35°C, there was a significant increase from day 3 to day 28, then a decrease to day 96 in measured MPA concentration. At 21°C, there was a progressive increase in concentration from 7 to 96 days of storage (P < 0.0001). At 4°C and -20°C, plasma samples were stable for 28 days after collection, but at -20°C, there was a subsequent median increase in concentration of 15.2% at day 96.
Samples should be separated as soon as practicable after collection and stored at -20°C or 4°C before transport to the analytical laboratory using subambient temperatures if possible.
免疫抑制剂霉酚酸（MPA）广泛用于实体器官移植，并越来越多地用于血液学疾病和自身免疫性疾病。浓度监测通常仅限于与移植中心相关的专门实验室，样本会被送到那里，从患者到当地实验室以及从那里到专门实验室都可能存在延迟。血浆中霉酚酸葡萄糖醛酸酯的不稳定性已有详细描述，但关于患者样本中 MPA 稳定性的数据有限，特别是在全血中。本研究旨在评估患者样本中 MPA 的稳定性，并确定用于治疗药物监测的正确样本类型和最佳运输条件。
在采血后 2 小时内送到实验室进行 MPA 估计的全血样本被等分，分离并储存在一系列温度下，这些温度旨在模拟本实验室中观察到的运输时间和条件范围。10 份全血样本在 4°C、21°C 或 35°C 下最多储存 4 周，血浆在-20°C、4°C、21°C 和 35°C 下储存。通过液相色谱-串联质谱法测量 MPA 浓度。
在 35°C 的全血中，随着时间的推移，MPA 浓度中位数显著增加（P=0.004），但一些样本的浓度下降。在 21°C 和 4°C 下，增加幅度较小（P=0.04 和 0.02）。在 35°C 的血浆中，从第 3 天到第 28 天，然后在第 96 天，测量的 MPA 浓度显著下降。在 21°C 下，从储存的第 7 天到第 96 天，浓度逐渐增加（P<0.0001）。在 4°C 和-20°C 下，采集后 28 天内血浆样本稳定，但在-20°C 下，第 96 天浓度中位数增加 15.2%。
样本应在采集后尽快分离，并在运输到分析实验室之前，在-20°C 或 4°C 下储存，如果可能的话，在亚环境温度下储存。
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