为什么凝血检测样本必须要离心15分钟？ Why do coagulation test samples have to be centrifuged for 15 minutes?
Friends who have just entered the testing circle have always had a question: why do coagulation test samples have to be centrifuged for 15 minutes? Other biochemical immune samples can be centrifuged for 5-10 minutes, and even some laboratories directly compress the sample centrifugation time to 3 minutes in order to save time.
With the development of medical testing technology, more and more laboratories have used automated assembly lines and robots.
In the so-called overall solution, many people are trying to connect the equipment that can be connected to the assembly line in the laboratory, and the whole "unmanned laboratory" is good?
However, in the process of practical operation, it is inevitable to encounter many problems to be solved, friends who have done laboratory assembly lines know that almost all inspection lines on the market are facing a bottleneck: the efficiency of the centrifuge can not be broken, commonly known as the "short board effect".
Therefore, the centrifugation problem of coagulation test samples has also become an insurmountable obstacle for major assembly line manufacturers. So why are coagulation test samples so demanding for centrifugation? Let's start by looking at how industry standards and guidelines are stated.
CLSI H21-ED6 (2024) "Collection, transportation and processing of blood samples for plasma coagulation tests" specifies that:
Isolation of platelet-deficient plasma (platelet count < 10*10^9/L) is critical when performing plasma coagulation testing, especially for LAs, heparin monitoring, or follow-up testing after plasma cryostorage. To obtain standard PPP, the most common centrifugation condition is 1500 g at room temperature for 15 min. It should be noted here that it is 1500g, not 1500 rpm.
The International Committee for Standardization of Hematology (ICSH) Recommendations for the Processing of Blood Samples for Coagulation Testing (2021) states:
建议 5.1：用于凝血检测的血液样本应在18-24°C的环境温度下离心，使用的离心条件应足以获得残余血小板计数<10*10^9/L的乏血小板血浆。
Recommendation 5.1: Blood samples for coagulation testing should be centrifuged at an ambient temperature of 18-24°C, and centrifugation conditions should be sufficient to obtain platelet-deficient plasma with a residual platelet count <10*10^9/L.
备注：这通常可以1500g离心15分钟或者以1700g离心10分钟来实现，并且应每6-12个月对乏小板血浆进行血小板计数检查验证。
Note: This can usually be achieved with 1500 g centrifugation for 15 minutes or 1700 g for 10 minutes, and platelet count verification should be performed on platelet-deficient plasma every 6 to 12 months.
建议 5.2：用于狼疮抗凝物检测的样本和用于APTT或抗Xa检测的含有UFH的样本应在第一次离心之后，在冷冻之前进行第二次离心。
Recommendation 5.2: Samples for lupus anticoagulant testing and UFH-containing samples for APTT or anti-Xa testing should be centrifuged for a second time after the first centrifugation and prior to freezing.
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"WS/T 359-2024 Specimen collection and processing of commonly used items in thrombosis and hemostasis" stipulates:
It can be seen that the centrifugation standard is unified, and the purpose of centrifugation is to obtain platelet-deficient plasma (PPP), so the question arises again, why must PPP be used? This has to start with the principle of coagulation testing.
In fact, those who are familiar with the theory of coagulation falls know why PPP is used, because of phospholipids.
Platelet factor 3 (PF3) is a kind of membrane surface phospholipid formed during platelet activation, which is an important part of human coagulation and a fixed site of coagulation factor V, which can accelerate the production of thromboplastin and promote the coagulation process.
The coagulation assays we use such as PT and APTT contain synthetic phospholipids, platelet-deficient plasma mixed with phospholipids, and the coagulation pathway is activated by activators and Ca2+ ions.
血小板上有磷脂，活化的血小板还会释放能中和肝素的血小板第4因子（PF4），影响抗凝检测，同时还有20%的V因子来源于血小板，影响测定凝血时间；最重要的是狼疮抗凝物会与血小板上的磷脂结合，导致假阴性，同时缩短APTT时间；有研究显示，非标准乏血小板血浆情况下，中等浓度狼疮抗凝物质存在会导致APTT缩短10秒。
There are phospholipids on platelets, and activated platelets also release platelet factor 4 (PF4), which can neutralize heparin, which affects anticoagulation detection, and 20% of factor V comes from platelets, which affects the coagulation time. Most importantly, lupus anticoagulants bind to phospholipids on platelets, resulting in false negatives while shortening the APTT time; Studies have shown that the presence of moderate concentrations of lupus anticoagulant in non-standard platelet-deficient plasma results in a 10-second shortening of APTT.
所以如此严格的离心力和离心时间就是为了得到标准的乏血小板血浆，以确保在检测过程中没有自身磷脂的干扰，从而获得最准确的检测结果。
Therefore, such strict centrifugal force and centrifugation time are to obtain standard platelet-deficient plasma to ensure that there is no interference from its own phospholipids during the detection process, so as to obtain the most accurate test results.
一切为了患者，也为了自己，小伙伴们就不要偷懒了，赶紧把离心机的离心力和离心时间调回去吧。
All for the sake of the patients and for themselves, don't be lazy, hurry up and adjust the centrifugal force and centrifugation time of the centrifuge back.
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