D-dimer (D-dimer) clinical application 2.0

D-dimer (D-dimer), as a classic thrombosis marker, is widely used in clinical practice to exclude diseases such as venous thromboembolism (VTE), diagnosis and treatment monitoring of disseminated intravascular coagulation (DIC), malignant tumors and other diseases.
and the evaluation of coagulation disorders, which has become one of
the most "enthusiastic" coagulation tests for doctors.

However, with the release of many clinical application studies on D-dimer in recent years, according to the characteristics of D-dimer itself and the association of clinical diseases, the application scope of D-dimer has been greatly expanded, and this article will take you to understand D- A new chapter in
the clinical application of dimers.

First, the theoretical basis of D-dimer clinical application

The reason why D-dimer dynamic monitoring can be used to predict thrombosis and evaluate anticoagulant effect is inseparable from the following characteristics
in its clinical application.

D-dimer is a degradation product of crosslinked fibrin, the production of which reflects the activation
of the body's coagulation and fibrinolytic systems.
The detection of an elevated D-dimer indicates that activation of the coagulation system and the fibrinolytic system must have occurred in the body
.
Therefore, D-dimer is also considered one of
the sensitive markers of pre-thrombotic or hypercoagulable state.

The formation process of D-dimer

Usually, the increase in D-dimer level is detectable about 2 hours after the thrombus begins to form, and the half-life of the generated D-dimer in the body is about 7-8h.
It is easy to detect without losing its monitoring significance, and has a good match with clinical practice
.

Second, the traditional clinical application of D-dimer

Negative exclusion of thrombotic disorders: D-dimer testing in combination with clinical risk assessment tools (Wells score, etc.
) can be used efficiently for deep vein thrombosis (DVT) and pulmonary embolism (PE).
) (as shown below).

Application of D-dimer in VTE diagnostics

In patients with acute PE, the higher the D-dimer value, the higher the PESI score (PE Severity Index score) and the increased
mortality.
D-dimer< 1500 μg/L had a good negative predictive value of 3-month PE mortality: D-dimer< 3-month mortality at 1500 μg/L was 0%
。 D-dimer> 1500 μg/L should be highly vigilant
.

Figure 1: Diagnostic flow of deep vein thrombosis (DVT).

Diagnosis of disseminated intravascular coagulation (DIC): the pathogenesis of DIC is manifested by hyperfibrinolytic system, FDPs and D-dimer in DIC patients It will increase significantly (more than 10 times).

In the diagnostic guidelines or consensus of DIC at home and abroad, D-dimer is used as one of the laboratory indicators for the diagnosis of DIC, and the degree of increase in D-dimer level is in The DIC scoring system occupies an important position, of course, the diagnosis of DIC needs to be combined with the patient's clinical condition and other laboratory indicators
.

D-dimer levels in special populations:

(1) Elderly population: The level of D-dimer in healthy people will increase with age, the level of women is slightly higher than that of men, and the level of pregnant women will increase
significantly.
Several studies currently recommend a CUT-OFF value for negative exclusion in patients with VTE: 500 ng/ml (FEU) for people under 50 years of age ) as; People over 50 years old use Age*10ng/ml (FEU).

(2) Pregnancy: The level of D-dimer in pregnant women will increase physiologically, and with the increase of gestational age, the positive proportion and absolute level of D-dimer will gradually increase
.
The mechanism of D-dimer elevation during pregnancy is more complex: 1) progesterone in pregnant women will stimulate the liver to synthesize coagulation factors and reduce the synthesis of anticoagulant proteins; 2) Fetal compression causes obstruction of inferior vena cava return and slows down blood flow; 3) In the third trimester, with the increase of uterine maturity, the rupture of the uterine spiral artery releases tissue factors and other procoagulant substances, which makes the pregnant woman's body show a tendency to hypercoagulability; 4) A small number of pregnant women have other thrombophilic factors, such as antiphospholipid syndrome
.

D-dimer Clinical Application 2.
0

D-dimer dynamic monitoring predicts VTE formation

D-dimer has a predictive effect
on recurrent VTE.
The 3-month recurrence rate in D-dimer-negative patients is 0
.
If D-dimer is elevated again during follow-up, the risk of VTE recurrence can be significantly increased
.
The half-life of D-dimer in vivo of 7-8 hours makes it possible for
D-dimer dynamic monitoring to predict the risk of venous thromboembolism.
For transient hypercoagulable states or microthrombosis, D-dimer decreases rapidly after a mild elevation, theoretically within 24 hours, and the resulting D-dimer undergoes 3-4 hours half-life, which can be reduced by 50%-90%.

However, when there is continuous new thrombosis in the body, the D-dimer in the body will continue to rise, showing a "several" shape increase curve.

Therefore, for specific patients, especially acute and severe and postoperative patients, if there is a rapid increase in D-dimer level, we should be alert to the possibility of
thrombosis.