APTT elevated - what does it mean?
APTT is an activated partial thromboplastin time. This indicator is always measured when performing a blood coagulogram, as it gives an assessment of its coagulation system. This assay was discovered in 1953 and quickly entered medical laboratory practice.
APTT is often measured in parallel with an indicator such as PTT (prothrombotic time). If APTT indicates the effectiveness of the internal pathway of blood coagulation, then PTT characterizes the external pathway of activation. Sometimes APTT is replaced by the abbreviation APTT (activated partial thromboplastic time) or by the term cephalin-kaolin time. However, they all mean the same thing - the time during which the blood clotting in the tested person.
- APTT rate indicators
- Pregnancy and APTT level
- Low and high APTT - what does this mean?
- When do I need to donate blood to determine the APTT index?
APTT rate indicators
The APTT value depends on the amount of plasma blood factors II, V, VII, X, XI, XII and fibrinogen. To determine the time of formation of a blood clot, an anticoagulant is injected into the plasma, which deprives it of platelets, and then cephalin-kaolin reagent and CaCl2 are added. Tissue factor is not used in this laboratory study, therefore the test is called "partial".
Time measurements are taken in seconds. Different medical sources may indicate different indicators of the APTT rate, since each laboratory has its own reference parameters. The average values of the norm, which clinicians are guided by, are in the range from 24 to 35 seconds. If the clot formation time is shortened by more than 5 seconds from the suggested normal limits, for example, is 19 seconds, then this indicates an activated patient's internal coagulation system. Simply put, his blood clots faster than necessary. This condition is called hypercoagulation.
If the time is extended to 40 seconds or more, then the test person's blood clotting more slowly than it should be. This condition is called hypocoagulation. Hypocoagulation develops when fibrinogen or plasma factors II, V, VII, X, XI, XII are lowered.
This can happen under the following conditions:
In the body, the liver membrane (its parenchyma) is damaged in those places where K-dependent blood coagulation factors are formed.
- The patient has a lack of vitamin K in the body, which is necessary for the synthesis of most factors.
- A large amount of heparin circulates in the human blood.
- Lupus anticoagulant is present in the blood.
- There are substances in the blood that prevent fibrin monomers from polymerizing.
If it takes more time to form a clot, then the APTT is considered elevated. If it takes less time to form a clot, then this indicates an excessive activity of blood factors, which means that the APTT will be reduced.
So, high APTT values indicate that a person has a risk of developing bleeding, and it can begin even when the body is exposed to the slightest provocative factors. A low APTT level indicates a high risk of thrombosis and thromboembolism. Therefore, doctors attach such great importance to this test, because, along with other indicators of the coagulogram, it can provide enough information about human health.
Pregnancy and APTT level
A coagulogram is prescribed for a pregnant woman every three months. This analysis must be taken in order for the doctor to have maximum information about her state of health. Indeed, at this time, a restructuring of the hormonal background occurs, another circle of blood circulation is formed, which delivers food to the child. This circle is called the uteroplacental circle. In addition, the body prepares for the fact that in the near future it will have to lose a certain part of the blood. Therefore, the changes affect the entire hemostatic system.
Any pathology of the blood coagulation system during pregnancy is doubly dangerous than during normal times. This is almost always associated with the risk of serious complications. Therefore, doctors closely monitor APTT and other blood counts. In the blood of a pregnant woman, there is an increase in the level of fibrinogen, which can reach a value of 6.0 g / l, and the APTT can be shortened in comparison with those of a non-pregnant woman.
The range of normal APTT values in pregnant women ranges from 14-20 seconds. More accurate values are determined in the specific laboratory where the study is carried out.
If the APTT time is shortened, then the likelihood of blood clots formation increases. In women in position, these risks increase several times. Blood clots can form anywhere, but if they form in the vessels of the placenta, it can lead to premature detachment.
An increase in APTT promotes excessive blood thinning, which increases the likelihood of uterine bleeding. This condition is dangerous not only for the pregnant woman herself, but also for her unborn child.
Also, with changes in the APTT values, there is a risk of developing such a dangerous complication as disseminated intravascular coagulation. First, blood clots form in the woman's blood, and then the blood stops clotting. This threatens massive blood loss, which is very difficult to stop.
DIC syndrome is poorly corrected with drug therapy. This condition is an urgent problem in modern obstetrics and gynecology, as it can cause death.
Even if a woman is absolutely healthy, but is in position, she is prescribed a blood coagulogram every 3 months. This allows you to control the hemostasis system, and therefore monitor the health of the woman and the fetus. In the presence of any diseases or risks, the analysis is performed as often as necessary to provide adequate treatment. Indications for unscheduled blood donations for analysis are previously suffered miscarriages, the fact of the birth of a stillborn child, the presence of preeclampsia, and increased uterine tone.
Low and high APTT - what does this mean?
A decrease in the APTT level indicates that the blood in the body is clotting too quickly.
The following conditions will lead to hypercoagulation of blood:
- Developing DIC syndrome. However, rapid blood clotting is characteristic only of the first stage of development of this most dangerous condition.
- Thromboembolism of the vessel, regardless of its location. This can be the heart, lungs, brain and spinal cord, renal artery, etc.
- Developing thrombosis of the arteries supplying the placenta, which leads to its premature detachment. As a result, the child may die while still in the womb.
It should be noted that an increase in APTT does not always indicate a pathological condition in a pregnant woman. Sometimes this indicator turns out to be overestimated in the case when tissue thromboplastin gets into the blood sample. Most often this occurs in a situation where blood from a vein cannot be taken immediately, which forces the laboratory assistant to perform manipulations several times, injuring the surrounding tissues.
An increase in the APTT level contributes to the fact that the blood clots slowly.
This can be observed against the background of the following violations:
- All types of hemophilia: hemophilia type A, type B and type C. In the first case, there is a deficiency of antihemophilic globulin (FVIII), in the second case, a person will have a lack of Christmas factor (XI), and in the third case, a deficiency of factor XI.
- Circulation of factors in the blood that interfere with the process of blood clotting. This condition is called inhibitory hemophilia.
- Von Willebrand disease.
- Progressive disseminated intravascular coagulation syndrome, which is in the second or third stage of development.
- Treatment with high molecular weight heparins.
- Severe damage to the liver parenchyma.
- Antiphospholipid syndrome.
However, as in the case of a low APTT level, it can also be increased by errors in the analysis. For example, if there was not enough water in the test tube to perform the study.
When do I need to donate blood to determine the APTT index?
Coagulogram is prescribed to patients quite often. This analysis is aimed at assessing the hemostasis system, therefore, doctors of various specialties recommend that their patients undergo the study.
So, a coagulogram can be prescribed for the following purposes:
- Screening of the hemostasis system in patients who are at risk for the development of various diseases associated with the hematopoietic system.
- Diagnosed disorders in the blood coagulation system.
- Taking certain medications that affect the hemostatic system.
- The period of bearing a child.
- The need to calculate the dose of high molecular weight heparins for treatment, or therapy using direct anticoagulants.
- Revealing DIC syndrome.
- Suspected hemophilia.
- Antiphospholipid syndrome.
APTT is one of the most important blood parameters. Knowledge of the rate of activated partial thromboplastin time allows specialists to timely detect and correct various diseases.
The author of the article: Shutov Maxim Evgenievich | Hematologist
Education: In 2013 he graduated from the Kursk State Medical University and received a diploma "General Medicine". After 2 years, completed residency in the specialty "Oncology". In 2016 completed postgraduate studies at the National Medical and Surgical Center named after N. I. Pirogov.