Two key blood coagulation studies, activated partial thromboplastin time (APTT) and prothrombin time (PT), both help determine the cause of coagulation abnormalities.
To keep the blood in a liquid state，The body must perform a delicate balancing act. Circulating blood contains two blood components, procoagulant, which promotes blood coagulation, and anticoagulant, which inhibits coagulation, to maintain blood flow. However, when a blood vessel is damaged and the balance is disturbed, procoagulant collects in the damaged area and blood clotting begins. The process of blood coagulation is a link-by-link, and it can be activated by any two coagulation systems in parallel, intrinsic or extrinsic. The endogenous system is activated when blood contacts collagen or damaged endothelium. The extrinsic system is activated when damaged tissue releases certain coagulation substances such as thromboplastin. The final common path of the two systems leading to the condensation apex. When this coagulation process, although it appears to be instantaneous, two key diagnostic tests, activated partial thromboplastin time (APTT) and prothrombin time (PT), can be performed. Doing these tests helps to make a substantial diagnosis of all coagulation abnormalities.
1. What does APTT indicate?
The APTT assay evaluates endogenous and common coagulation pathways. Specifically, it measures how long it takes for a blood sample to form a fibrin clot with the addition of an active substance (calcium) and phospholipids. More sensitive and faster than partial thromboplastin time. APTT is often used to monitor treatment with liver violet.
Each laboratory has its own normal APTT value, but generally ranges from 16 to 40 seconds. Prolonged time may indicate insufficiency of the fourth domain of the endogenous pathway, Xia or factor, or deficient factor I, V or X of the common pathway. Patients with vitamin K deficiency, liver disease, or disseminated intravascular coagulopathy will prolong the APTT. Certain drugs—antibiotics, anticoagulants, narcotics, narcotics, or aspirin can also prolong APTT.
Decreased APTT can result from acute bleeding, extensive sores (other than liver cancer) and some drug treatments including antihistamines, antacids, digitalis preparations, etc.
2. What does PT show?
The PT assay evaluates extrinsic and common clotting pathways. For monitoring treatment with anticoagulants. This test measures the time it takes for plasma to clot after the addition of tissue factor and calcium to a blood sample. A typical normal range for PT is 11 to 16 seconds. Prolongation of PT may indicate a deficiency of thrombin profibrinogen or factor V, W or X.
Patients with vomiting, diarrhea, eating green leafy vegetables, alcohol or long-term antibiotic therapy, antihypertensives, oral anticoagulants, narcotics, and large doses of aspirin can also prolong PT. Low-grade PT can also be caused by antihistamine barbiturates, antacids, or vitamin K.
If the patient's PT exceeds 40 seconds, intramuscular vitamin K or fresh-dried frozen plasma will be required. Periodically assess the patient's bleeding, check his neurological status, and do occult blood tests in urine and feces.
3. Explain the results
A patient with abnormal coagulation usually needs two tests, APTT and PT, and he will need you to interpret these results, pass these time tests, and finally arrange his treatment.