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凝血系统，医学中的重中之重，但学起来却是难之又难。先别说一堆凝血因子，搞懂八百遍就能忘掉八百遍，单一张凝血级联反应的图，看多少次都觉得是鬼画符一般的存在。对我这种脑容量不足的人来说，单靠死记硬背来记忆各项指标的名字及临床应用，效果自然是不好。比如属于我常记常忘那一系列的几项凝血功能的化验，不论中文名还是英文名都长得极为相像。凝血酶原、凝血酶、活化部分凝血活酶、PT、TT、APTT，一不小心就会看错。另外，“凝血活酶”是什么东西？为什么要加上“部分”两个字？更多关于凝血途径的详细内容和各检查的临床意义，可进入下列网址查看：https:///the-coagulation-cascade/https://www./pt-ptt-and-inr-results-3157005 
（图片源自MDPI，侵删）
先复习一下凝血途径： ①外源性 extrinsic pathway，血管损伤，血液暴露于血管外组织所释放的组织因子而被激活，凝血过程速度快； ②内源性 intrinsic pathway，血管内膜损伤，导致血液与带负电荷的异物表面接触而启动凝血过程，完全依赖血管内的凝血因子，凝血速度慢。 ③共同通路 common pathway，凝血酶原酶复合物（prothrombinase complex）使凝血酶原→凝血酶，凝血酶再使纤维蛋白原→纤维蛋白，从而形成稳定的血栓thrombus。 
PT: Prothrombin Time 凝血酶原时间
aPTT：activated Partial Thromboplastin Time 活化部分凝血活酶时间 TT: Thrombin Time 凝血酶时间 这几个词里面都有thromb-这个词根
 thromb-: reflecting a New Latin combining form, from the Ancient Greek θρόμβος (thrómbos, “lump”, “piece”, “blood clot”, “milk curd”).由thromb-词根所衍出的词有：血栓Thrombus、凝血酶thrombin、抗凝血酶antithrombin、血小板thrombocyte（即能形成血栓的细胞）等等，总之，都跟凝血、血栓有关。pro-：From Ancient Greek πρό (pró, “before”). 即earlier; priorpro thrombin：即形成thrombin的前体，即凝血酶原。aPTT，核心在于thromboplastin这个词，中文翻译成凝血活酶。凝血活酶和凝血酶显然不是同一种东西，那它们有什么区别？部分凝血活酶又是什么？Thromboplastin：Thromboplastin is a plasma protein aiding blood coagulation through catalyzing the conversion of prothrombin to thrombin. It is a complex enzyme that is found in brain, lung, and other tissues and especially in blood platelets and that functions in the conversion of prothrombin to thrombin in the clotting of blood—called also thrombokinase.大概的描述就是“可以使血液凝固的一种血浆蛋白”，更进一步的描述，这种物质是一种复合酶，可以激活凝血酶原转化为凝血酶。所以，使凝血酶原“活化”为凝血酶，是这种物质的主要功能，所以翻译为凝血活酶。Complete thromboplastin consists of tissue factor（组织因子，TF ，Factor III）, phospholipids, and CaCl2 to reintroduce calcium ions that were chelated by sodium citrate originally used to prevent coagulation of the sample blood during transportation and/or storage.完整的凝血活酶包括组织因子、磷脂，所以，如果血液中加入完整的凝血活酶，因为其中包含组织因子，所以激活的是外源性凝血途径（extrinsic pathway），所测得的血液凝固所需的时间就是所谓的prothrombin time，PT， 凝血酶原时间。由下面这段话也可以看的出来，thromboplastin time=prothrombin time。之所以叫做prothrombin time，是因为凝血时间（主要）依赖由肝脏产生的prothrombin的水平。Thromboplastin time (prothrombin time) is meant the time required for coagulation after the addition of an optimum amount of Ca2 and excess thromboplastin to blood plasma. The prothrombin time (PT) test measures how long it takes for a blood clot to form based on a protein produced by the liver called prothrombin. Along with its derived measures of international normalized ratio (INR), they are assays evaluating the extrinsic pathway of coagulation. They are used to determine the clotting tendency of blood, in the measure of warfarin dosage, liver damage, and vitamin K status. 凝血酶原时间是指在缺乏血小板的血浆中加入过量的组织凝血活酶和钙离子，凝血酶原转化为凝血酶，导致血浆凝固所需的时间。国际标准化比值 INR=（患者PT值/正常PT值）^ISI，用于华法林治疗剂量的指导。partial thromboplastin 是什么意思？ 如果人为将thromboplastin里面的组织因子去掉（不完整了，所以是部分partial），即为partial thromboplastin，血液里加入partial thromboplastin后血液凝固所需的时间，即为partial thromboplastin time，PTT，部分凝血活酶时间，激活的是内源性凝血途径（intrinsic pathway）。在PTT前再加actived，意思是测量时除了要加入部分凝血活酶，还需要加入活化接触因子激活剂（带负电荷），如白陶土、硅藻土等。
Thromboplastin is the combination of both phospholipids and tissue factor, both needed in the activation of the extrinsic pathway. However, partial thromboplastin is just phospholipids, and not tissue factor. Partial thromboplastin was used to measure the intrinsic pathway. This test is called the aPTT, or activated partial thromboplastin time. TT，Thrombin Time，凝血酶时间，是指人为加入足量凝血酶后血液凝固所需的时间，也就是说，测量的是common pathway中纤维蛋白原（fibrinogen）形成纤维蛋白（fibrin）的能力，受纤维蛋白原的数量及功能、纤维降解产物（fibrindegradation products）水平的影响。The thrombin time (TT) is a blood test that measures the time it takes for a clot to form in the plasma of a blood sample, after an excess of thrombin has been added. It is used to diagnose blood coagulation disorders and to assess the effectiveness of fibrinolytic therapy. If the time it takes for the plasma to clot is prolonged, a quantitative (fibrinogen deficiency) or qualitative (dysfunctional fibrinogen) defect is present. 
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