Editing Partial thromboplastin time (section)

==Methodology==
[[File:Blue Top.JPG|thumb|Blue Top Vacutainer tube (sodium citrate vial) used for PT and PTT blood tests]]

Activated partial thromboplastin time (APTT) is typically analyzed by a medical technologist or laboratory technician, either manually or using an automated instrument at 37°C, which approximates normal human body temperature. [[Prothrombin time]] utilizes complete [[thromboplastin]], a combination of [[tissue factor]] and [[Phospholipid|phospholipids]]. In contrast, APTT employs partial thromboplastin, containing only phospholipids and no tissue factor—hence the term "partial thromboplastin time." An activator is used in the APTT test to initiate the intrinsic pathway of blood coagulation. Common activators include kaolin, silica, celite, and ellagic acid.<ref>{{Cite journal |last=Bates |first=Shannon M. |last2=Weitz |first2=Jeffrey I. |date=2005-07-26 |title=Coagulation Assays |url=https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.104.478222 |journal=Circulation |language=en |volume=112 |issue=4 |doi=10.1161/CIRCULATIONAHA.104.478222 |issn=0009-7322}}</ref>
* Blood is drawn into a [[test tube]] containing [[oxalate]] or [[citrate]], molecules which act as an [[anticoagulant]] by binding the calcium in a sample. The blood is mixed, then centrifuged to separate blood cells from plasma (as partial thromboplastin time is most commonly measured using [[blood plasma]]).
* A sample of the plasma is extracted from the test tube and placed into a measuring test tube.
* Next, an excess of [[calcium]] (in a [[phospholipid]] suspension) is mixed into the [[blood plasma|plasma]] sample (to reverse the anticoagulant effect of the citrate enabling the blood to clot again).
* Finally, in order to activate the [[Coagulation#Intrinsic pathway|intrinsic pathway]] of coagulation, an activator is added, and the time the sample takes to clot is measured optically. Some laboratories use a mechanical measurement, which eliminates interferences from lipemic and [[icteric]] samples.