- What is it for
- How is done
- Coagulogram tests
- 1. Bleeding time (TS)
- 2. Prothrombin time (TP)
- 3. Activated Partial Thromboplastin Time (APTT)
- 4. Thrombin time (TT)
- 5. Amount of platelets
The coagulogram corresponds to a group of blood tests requested by the doctor to evaluate the blood clotting process, identifying any changes and thus indicating the treatment for the person in order to avoid complications.
This test is requested mainly before surgery to assess the patient's risk of bleeding during the procedure, for example, and involves bleeding time, prothrombin time, activated partial thromboplastin time, thrombin time and evaluation of the amount of platelets.
What is it for
The coagulogram is indicated mainly before surgery, but it can also be requested by the doctor to investigate the cause of hematological diseases and to check the risk of thrombosis, especially in women who use contraceptives.
In addition, the coagulogram is indicated after the bite of an animal that has toxin that can interfere in the coagulation process and in the monitoring of people who use anticoagulants, such as Heparin and Warfarin, for example. Meet other anticoagulants and when they are indicated.
How is done
The coagulogram must be done with the person fasting for 2 to 4 hours and consists of collecting a blood sample that is sent for analysis, with the exception of the Bleeding Time (TS), which is done on the spot and consists of observing the time it takes for bleeding to stop.
It is important that before the exam is performed, the use of anticoagulant drugs is informed, since it can interfere with the result or be taken into account when analyzing, for example. Thus, it is important to have guidance from the doctor regarding the suspension of the use of the drug before performing the coagulogram.
Coagulogram tests
The coagulogram consists of some tests that assess the presence of all the factors involved in blood clotting and, consequently, hemostasis, which corresponds to the processes that happen inside the blood vessels that aim to keep the blood fluid in order to avoid the formation clots or bleeding. Understand everything about hemostasis.
The main exams present in the coagulogram are:
1. Bleeding time (TS)
This exam is usually requested as a way to complement the other exams and is useful to detect any change in platelets and is done by making a small hole in the ear, which corresponds to the Duke technique, or by cutting the forearm, called the Ivy technique, and then counting the time when bleeding stops.
To do the Ivy technique, pressure is applied to the patient's arm and then a small cut is made at the site. In the case of Duke's technique, the hole in the ear is made using a lancet or a disposable stylus. In both cases, bleeding is assessed every 30 seconds using a filter paper, which absorbs blood from the site. The test ends when the filter paper no longer absorbs blood.
Through the TS result, it is possible to assess hemostasis and the presence or absence of von Willebrand factor, which is a factor present in platelets that plays a fundamental role in the blood clotting process. Although this test is useful in detecting changes in hemostasis, it can cause discomfort especially in children, as the test can be done by making a hole in the ear, for example.
How to understand the result: After drilling the hole, the doctor or technician responsible for the examination counts the time that the blood coagulates and monitors using a filter paper that absorbs the blood from the location. When the filter paper no longer absorbs the blood, the test is terminated. If the test was done using the Ivy Technique, which is the arm, the normal bleeding time is between 6 and 9 minutes. In the case of the Duke technique, which is that of the ear, the normal bleeding time is between 1 and 3 minutes.
When the time is longer than the reference time, it is said in the extended TS exam, indicating that the coagulation process took longer than normal, which may be indicative of von Willebrand's disease, use of anticoagulant drugs or thrombocytopenia, for example. Know the main causes of thrombocytopenia.
2. Prothrombin time (TP)
Prothrombin, also known as Coagulation Factor II, is a protein that is activated during the coagulation process and whose function is to promote the conversion of fibrinogen into fibrin, forming the secondary or definitive platelet plug.
This test aims to verify the functioning of the extrinsic coagulation pathway, as it consists of assessing the time it takes the blood to form the secondary plug after exposure to calcium thromboplastin, which is the reagent used in the test.
How to understand the result: In normal conditions, after blood contact with calcium thromboplastin, the extrinsic pathway is activated, with activation of factors VII and X of coagulation and, consequently, factor II, which is prothrombin, promoting the conversion of Fibrinogen in Fibrin, stopping bleeding. This process normally takes between 10 and 14 seconds.
However, in some situations the coagulogram detects enlarged PT, which means that prothrombin activation occurs in a longer time than normal. Increased PT values usually occur when anticoagulants are used, vitamin K deficiency, factor VII deficiency and liver problems, for example, since prothrombin is produced in the liver.
In rare cases, PT may be decreased, as in the case of the use of vitamin K supplements or birth control pills with estrogen, for example. Understand more about the Prothrombin Time test result.
3. Activated Partial Thromboplastin Time (APTT)
This test is also used to assess hemostasis, however it allows the presence or absence of coagulation factors present in the intrinsic pathway of the coagulation cascade to be verified.
APTT is usually important to monitor patients who use Heparin, which is an anticoagulant, or who have problems with blood clotting, being useful to identify changes related to clotting factors.
In this examination, a sample of the collected blood is exposed to the reagents, and then the time it takes for the blood to clot is calculated.
How to understand the result: Under normal conditions, APTT is 21 to 32 seconds. However, when the person uses anticoagulants, such as heparin, or has a deficiency of specific factors of the intrinsic route, such as factors XII, XI or VIII and IX, which are indicative of hemophilia, the time is usually longer than the reference time., being indicated in the exam that the APTT is extended.
4. Thrombin time (TT)
The thrombin time corresponds to the time necessary for the clot to form after the addition of thrombin, which is the necessary clotting factor for the activation of fibrinogen in fibrin, which guarantees the stability of the clot.
This test is very sensitive and is done by adding thrombin in low concentrations in the blood plasma, the coagulation time being influenced by the amount of fibrinogen present in the plasma.
How to understand the result: Normally after the addition of thrombin to the plasma, the clot forms between 14 and 21 seconds, this being considered the reference value, which may vary according to the laboratory in which the test is performed.
TT is considered prolonged when the person uses anticoagulants, presents fibrin degradation products, has factor XIII or fibrinogen deficiency, for example.
5. Amount of platelets
Platelets are fragments of cells present in the blood that play an essential role in hemostasis, since they contain important factors for the clotting process, such as von Willebrand factor, for example.
When there is a tissue injury, the platelets move quickly to the site of the injury, with the aim of assisting in the blood stagnation process. The activated platelets attach themselves to the endothelium of the injured vessel by means of von Willebrand factor and then alter its formation and release substances into the plasma to recruit more platelets to the injury site and thus form the primary platelet plug..
Thus, checking the amount of platelets is important in the coagulogram as it allows the doctor to know if there is a change in the process of primary hemostasis, recommending a more specific treatment.
How to understand the result: The normal amount of platelets in the blood is between 150000 and 450000 / mm³. Values lower than the reference value are indicated in the exam as thrombocytopenia, indicating that there is less amount of circulating platelets, which can result in blood clotting problems, favoring bleeding, in addition to being able to indicate nutritional deficiencies, changes in bone marrow or infections, for example.
Values above the reference are called thrombocytosis, which can result in excess clotting, which can happen due to lifestyle habits, such as smoking or alcoholism, for example, or due to pathological conditions, such as iron deficiency anemia, myeloproliferative syndrome and leukemia, for example. Learn about other causes of platelet enlargement.
