Clinical Laboratory, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA.
Arch Pathol Lab Med. 2011 Sep;135(9):1081-4. doi: 10.5858/2010-0488-OAR.1.
Clinical samples that have densities greater than that of separator gel in specimen tubes may exhibit gel flotation to the top of the specimen upon centrifugation. Inappropriate separator gel flotation can occur in specimens with high protein content. In automated analytical systems, gel flotation can lead to mechanical disruption and potential inaccurate result reporting upon aspiration into instrument sampling probes.
To determine the relative specimen densities and estimated total protein contents at which specimen gel flotation would occur upon centrifugation in commonly used commercial specimen tubes, a comparative study of separator gel density was initiated using prepared dextran solutions.
Specific gravity of several dextran solutions was determined by direct hydrometry. The dextran solutions were introduced to serum and plasma lithium heparin BD Vacutainer specimen tubes manufactured by Becton, Dickinson and Company and into Vacuette specimen tubes manufactured by Greiner Bio-One containing separator gel. Following centrifugation the specimen tubes were examined for gel flotation.
Flotation was observed at a lower dextran solution density for Greiner than for BD tubes in both serum and plasma separator gel specimen tubes. Additionally, some differences between specimen tube lots were observed for both BD and Greiner tubes. The total protein content in clinical samples that would result in gel flotation can be estimated for different specimen container types.
Differences were observed for the gel separator specific gravity in different blood collection containers. Laboratories wishing to avoid problems with inappropriate gel flotation in high protein samples should consider these observations.
标本管中密度大于分离胶的临床标本在离心时可能会向上浮到标本顶端。高蛋白质含量的标本可能会发生不当的分离胶上浮。在自动化分析系统中，凝胶浮到顶端可能会导致在吸取到仪器采样探针时发生机械破坏和潜在的不准确结果报告。
为了确定在常用商用标本管中离心时标本发生凝胶上浮的相对标本密度和估计总蛋白含量，使用制备的葡聚糖溶液开始了对分离胶密度的比较研究。
通过直接比重计法确定几种葡聚糖溶液的比重。将葡聚糖溶液引入到由贝克顿、迪金森公司制造的血清和血浆锂肝素 BD Vacutainer 标本管以及含有分离胶的 Greiner Bio-One 的 Vacuette 标本管中。离心后检查标本管中是否有凝胶上浮。
在血清和血浆分离胶标本管中，Greiner 管的葡聚糖溶液密度较低时观察到浮胶，而 BD 管则没有。此外，BD 和 Greiner 管的不同管批之间也观察到了一些差异。对于不同的标本容器类型，可以估计导致凝胶上浮的临床样本中的总蛋白含量。
不同的血液采集容器中分离胶的比重存在差异。希望避免高蛋白样本中不当凝胶上浮问题的实验室应考虑这些观察结果。
