Piironen T, Pettersson K, Suonpää M, Stenman U H, Oesterling J E, Lövgren T, Lilja H
Department of Biotechnology, University of Turku, Finland.
Urology. 1996 Dec;48(6A Suppl):81-7. doi: 10.1016/s0090-4295(96)00616-4.
To study the in vitro stability of free and complexed forms of prostate specific antigen (PSA) in blood samples in order to establish guidelines for specimen handling, in particular for the clinical utility of the analysis of percentage free PSA.
Blood samples were collected and processed to generate serum, heparin plasma, and EDTA plasma. Three different two-site immunoassays were used to measure the concentrations of total PSA (PSA-T), free form of PSA (PSA-F), and PSA-alpha 1-antichymotrypsin complex (PSA-ACT) in order to determine the effect of repeated freezing and thawing, delayed separation of serum from blood cells, and stability during storage at 4 degrees C and 30 degrees C.
Five cycles of freezing and thawing introduced no statistically significant changes in the measured concentrations of PSA-T, PSA-F, or PSA-ACT. The effect of storing blood samples at room temperature for 1-6 h before separation of serum revealed a statistically significant decrease only for PSA-F after 5.5 h of storage (mean decrease 3.5%). PSA-T and PSA-ACT showed good stability in both serum and plasma samples, whereas PSA-F, after 1 week of storage at 4 degrees C, decreased on average by 28.8%, 7.8%, and 5.6%, respectively, in serum, heparin plasma, and EDTA plasma. The decreases of PSA-F at 4 degrees C were statistically significant (P < 0.05) relative to the controls (samples stored at -20 degrees C) after storage for 23 h in serum, 86 h in heparin plasma, and 71 h in EDTA plasma. When the same samples were stored at 30 degrees C for 24 h, only the mean decrease of PSA-F (4.8%) in serum was statistically significant.
PSA-F in blood samples is less stable than PSA-ACT. It is not advisable to store samples on the clot, especially if time and temperature cannot be controlled. Serum samples should be stored frozen if not analyzed during the same day. After thawing, samples can be stored up to 23 h at 4 degrees C prior to analysis. The use of plasma samples improves the stability of free PSA.
研究血液样本中游离及复合形式前列腺特异性抗原（PSA）的体外稳定性，以制定样本处理指南，特别是关于游离PSA百分比分析的临床应用。
采集血液样本并处理以获得血清、肝素血浆和乙二胺四乙酸（EDTA）血浆。使用三种不同的双位点免疫测定法测量总PSA（PSA-T）、游离形式PSA（PSA-F）和PSA-α1-抗糜蛋白酶复合物（PSA-ACT）的浓度，以确定反复冻融、血清与血细胞延迟分离以及在4℃和30℃储存期间的稳定性。
五个冻融循环对PSA-T、PSA-F或PSA-ACT的测量浓度未引入统计学上的显著变化。在血清分离前将血液样本在室温下储存1 - 6小时的影响显示，仅在储存5.5小时后PSA-F有统计学上的显著降低（平均降低3.5%）。PSA-T和PSA-ACT在血清和血浆样本中均显示出良好的稳定性，而PSA-F在4℃储存1周后，在血清、肝素血浆和EDTA血浆中分别平均降低28.8%、7.8%和5.6%。在血清中储存23小时、肝素血浆中储存86小时和EDTA血浆中储存71小时后，4℃下PSA-F的降低相对于对照组（储存在-20℃的样本）具有统计学显著性（P < 0.05）。当相同样本在30℃下储存24小时时，仅血清中PSA-F的平均降低（4.8%）具有统计学显著性。
血液样本中的PSA-F比PSA-ACT稳定性差。不建议将样本保存在凝块上，特别是如果时间和温度无法控制。如果当天未进行分析，血清样本应冷冻保存。解冻后，样本在分析前可在4℃下储存长达23小时。使用血浆样本可提高游离PSA的稳定性。
