D-dimer - What Is It? The Norm In Women, What To Do If It Is Increased?

2024 Author: Josephine Shorter | [email protected]. Last modified: 2024-01-17 02:10

D-dimer - what is it? Indicators of the norm

Scientists-hematologists suggest that the conversion of fibrinogen to fibrin occurs continuously in blood plasma. Since fibrin is the main constituent of blood clots, it would seem that this process should negatively affect the human body. However, this does not happen due to the coordinated work of the fibrinolytic and coagulation system. The fact is that fibrin threads dissolve under the action of the anticoagulant system, participating in the process of fibrinolysis. To track the functioning of the hemocoagulation system in clinical laboratory diagnostics, a special marker is used - D-dimer.

D-dimer are paired fragments of fibrinogen that allow observing the process of its formation and dissolution.

Content:

• D-dimer - what is it?
• Reasons for the appearance of D-dimer
• D-dimer rate, consequences of low and high values
• D-dimer in pregnancy
• What if the D-dimer is up or down?

D-dimer - what is it?

The use of D-dimer as a test for diagnosing the early stages of thrombus formation has been practiced since the 90s of the last century. The method began to be applied in practice as one of the main tests that allow early detection in laboratory conditions of conditions that predispose to the formation of blood clots. Such a feature of the D-dimer as the appearance of protein compounds after the disintegration of a blood clot was known 20 years before the use of this assay in practice, but the discovery did not receive practical significance due to the lack of knowledge of the method.

If earlier the definition of D-dimer was available only to specialized clinics, then in modern medicine any medical institution providing assistance in acute pathologies of hemostasis has equipment for the implementation of the technique. High-level emergency diagnostics helps to start treatment in a timely manner and save the health and lives of patients.

Reasons for the appearance of D-dimer

When hemostasis is activated, the process of fibrinolysis begins. Its main catalyst, plasmin, stimulates the breakdown of fibrin and fibrinogen. In addition to the predicted decay products - D- and E-fragments, by-products, dimers and trimers, are formed.

The appearance of D-dimers in the blood plasma indicates excessively active fibrinolysis. An intensive cleavage process indicates an increase in the blood clotting threshold and the accumulation of insoluble fibrin at the previous stages. If during the study of blood plasma D-dimers are found in it, then there is an increased risk of thrombosis, immediate measures should be taken to correct hemostasis.

D-dimer rate, consequences of low and high values

The D-dimer index test is a test of the activation of hemostasis at the highest level. The technique is rather complicated and is not included in the standard diagnostic set.

The normal concentration of the marker in the blood plasma of a healthy person is up to 0.5 μg / ml (500 ng / ml), or it is not detected at all, has negative values.

An increase in the D-dimer level above these indicators is a sign of the development of thrombosis, intravascular disseminated blood coagulation (DIC), deep vein thrombosis, and pulmonary embolism.

Conditions in which the level of D-dimer in plasma increases:

• Physiological changes during pregnancy;
• Acute inflammatory process;
• Infectious lesion of any etiology;
• Oncological disease;
• The consequences of thrombolytic therapy;
• Diseases leading to damage to the liver parenchyma;
• Thrombophilia in pregnancy or infertility;
• Ischemia, myocardial infarction;
• Large area hematomas, significant trauma;
• Operational interventions;
• Elderly age.

In 2% of cases, when the D-dimer values are significantly lower than normal with the presence of signs of thrombosis, it is necessary to find out the cause of the paradoxical results.

Reasons for low values:

• The minimum size of blood clots;
• Long exposure of the material for testing (more than 6 hours) in laboratory containers;
• Delayed testing;
• Lack of plasminogen or excessively high concentration of plasminogen activation inhibitor.

Applying the study of the level of D-dimers, it is possible to assess the degree of risk of thrombosis, disseminated intravascular coagulation syndrome, to track the dynamics of therapy for hemostasis pathologies. Despite the accuracy and information content of the technique, there is no need to wait for its results to start anticoagulant treatment. The therapy is carried out based on the clinical picture of the disease, without wasting time.

The study of the level of D-dimers is carried out at an increased risk of developing cardiovascular diseases (ischemia), suspicion of pathological processes in the hemostatic system.

D-dimer in pregnancy

Determining the level of fibrinogen in the blood plasma is of great importance in the management of pregnancy. The closer the due date, the higher these indicators. It should be borne in mind that an excessive increase in fibrinogen levels does not always fit into the norm, sometimes it is a sign of deep vein thrombosis.

Before childbirth and directly during childbirth, it reaches a maximum level, after 3 days it intensively declines, after 30-35 days it comes to standard values.

Table: D-dimer norm by day of pregnancy:

Gestational age	D-dimer values by week of pregnancy, normal in ng / ml	μg FEU / ml
Up to 13 weeks	Up to 280	Up to 0.56
13 - 20 weeks	100 - 700	0.2 - 1.4
21 - 28 weeks	150 - 850	0.3 - 1.7
29 - 35 weeks	150 - 1500	0.3 - 3.0
From 36 weeks to delivery	200 - 1550	0.4 - 3.1

1 μg FEU / ml = 500 ng / ml

In accordance with the data in the table, it can be concluded that during pregnancy, the concentration of the marker increases with an increase in gestational age. Deciphering its values will help prevent pathologies of pregnancy and childbirth, supplement the information obtained in the traditional analysis of the results of the coagulogram.

What if the D-dimer is up or down?

If the D-dimer test is negative, there is a high probability that the ability to thrombus in such a person is minimal. However, even with this result, there is a fraction of the likelihood that thromboembolism may appear. Even the most sensitive test has an error of no more than 1%, when the D-dimer is negative, but thrombosis is still present.

In case of positive results and a high level of D-dimer, it is necessary to perform in-depth diagnostics to detect deep vein thrombosis of the lower extremities or pulmonary artery. For this, vascular ultrasound and scintography are used. When interpreting test results, it is important to take into account the adjustment for age.

The result obtained is not always due to conditions that cause an ambiguous reaction of hemostasis, corresponds to reality, and this must also be taken into account.

Reasons for a high (false positive) value:

• Inflammatory processes in the body;
• The presence of neoplasms;
• Liver disease;
• Pregnancy;
• Recently suffered injuries and surgical interventions that mobilize the hemocoagulation system;
• Increased rheumatoid factor.

Reasons for low (negative) results:

• There are anticoagulants in the blood that prevent the formation of blood clots, or dissolve existing blood clots, which completely distorts the test results;
• The blood sample was taken incorrectly, after a short time after the formation of a thrombus or with a delay, in the first case the hemocoagulation system did not have time to respond, in the second case the blood sample was stored for too long.

A technical error can also give false results, for example, in the case of a discrepancy between the volume of blood taken and the volume of anticoagulant, although the percentage of such errors is extremely small. Modern analyzers and reagents for carrying out an express test are extremely sensitive, which makes it possible to detect serious pathologies associated with thrombus formation in time.

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.