Clotting time (also called Prothrombin time) is the time required for a sample of

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...

coagulate Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism o ...

in vitro ''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in biology an ...

under standard conditions. There are various methods for determining the

clotting Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism o ...

time, the most common being the

capillary A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter. Capillaries are composed of only the tunica intima, consisting of a thin wall of simple squamous endothelial cells. They are the smallest blood vessels in the body: ...

tube method. It is affected by calcium ion levels and many diseases. The normal range of clotting times is 2-8 minutes. For the measurement of clotting time by the test tube method, blood is placed in a glass test tube and kept at 37° C. The required time for the blood to clot is measured. There are several other methods, including testing for those on

blood thinners Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time. Some of them occur naturally in blood-eating animals such as leeches and mosquitoes, where the ...

, such as

heparin Heparin, also known as unfractionated heparin (UFH), is a medication and naturally occurring glycosaminoglycan. Since heparins depend on the activity of antithrombin, they are considered anticoagulants. Specifically it is also used in the treatm ...

warfarin Warfarin, sold under the brand name Coumadin among others, is a medication that is used as an anticoagulant (blood thinner). It is commonly used to prevent blood clots such as deep vein thrombosis and pulmonary embolism, and to prevent strok ...

. Activated

partial thromboplastin time The partial thromboplastin time (PTT), also known as the activated partial thromboplastin time (aPTT or APTT), is a blood test that characterizes coagulation of the blood. A historical name for this measure is the kaolin-cephalin clotting time ( ...

(aPTT) is used for heparin studies and the

normal range In medicine and health-related fields, a reference range or reference interval is the range (statistics), range or the interval (mathematics), interval of values that is deemed normal for a physiology, physiological measurement in healthy persons ...

is 20–36 seconds, depending upon which type of activator is used in the study.

Prothrombin time The prothrombin time (PT) – along with its derived measures of prothrombin ratio (PR) and international normalized ratio (INR) – is an assay for evaluating the ''extrinsic'' pathway and common pathway of coagulation. This blood test is als ...

(PT) is used for warfarin studies and the normal values differ for men and women. Adult male PT normal range is 9.6–11.8 seconds, while adult females' normal range is 9.5–11.3 seconds. Internationalized normalized ratio (INR) is also a warfarin study, with normal ranges of 2–3 for standard warfarin and 3–4.5 for high-dose warfarin. In a

veterinary Veterinary medicine is the branch of medicine that deals with the prevention, management, diagnosis, and treatment of disease, disorder, and injury in animals. Along with this, it deals with animal rearing, husbandry, breeding, research on nutri ...

study of bovine animals, the mean ACT was 145 seconds with a range of 120–180 seconds. Standard deviations were 18 and 13 for the first and second sampling, respectively. Repeatability of the ACT was acceptable.

References

Blood {{Hematology-stub