D-Dimer is a degradation product of cross-linked fibrin and an important marker of activation of the coagulation and fibrinolytic systems in the body. It is widely used in the diagnosis and treatment of diseases related to coagulation disorders.

The half-life of D-dimer in the body is approximately 8 hours, and it is mainly cleared from the circulation through the kidneys and reticuloendothelial system. There are various D-dimer detection systems in China, and there are large deviations in the results of different detection systems, which may lead to clinical misunderstandings of the detection results. The expert group compiled this consensus in order to solve the key problems faced by D-dimer in laboratory testing and provide a reference for the reasonable application and correct interpretation of D-dimer in clinical practice.

The use of monoclonal antibodies to recognize D-dimer epitopes in whole blood or plasma is the basic principle of D-dimer detection. Currently, the commercial D-dimer detection methods commonly used in clinical practice mainly include the following four types: whole blood agglutination detection method, enzyme-linked immunosorbent assay or enzyme-linked fluorescent assay, l latex enhanced immunoturbidimetric assay, and chemiluminescence method.

Table 1 Characteristics of different detection methods for D-dimer

The monoclonal antibodies selected by different kits have inconsistent affinity for the D-dimer in the mixed fragments, and the calibrator system cannot be traced. Therefore, it is recommended that the same medical institution should use the same D-dimer detection method and the same detection system, and test workers should be familiar with the D-dimer detection method, detection sensitivity and negative predictive value of the laboratory (highly recommended).

Sample factors, physiological state, and drug effects should always be considered when interpreting D-dimer test result (highly recommended).

The elements that should be provided in the D-dimer report include: normal reference interval, cut off value for venous thromboembolism (VTE) exclusion diagnosis (if verified), reporting method (FEU or DDU) and measurement unit (μg/L, mg/ L) (strongly recommended).

Venous thromboembolism (VTE) includes deep venous thrombosis (DVT) and pulmonary embolism (PE).

 D-dimer is used for the exclusion diagnosis of DVT of the lower limbs. The process is as follows:

Figure 2 Deep vein thrombosis (DVT) diagnostic flow chart

It is recommended that for patients with no obvious triggers for thrombosis, atypical clinical symptoms and signs, and low clinical possibility on Wells score, negative results of high-sensitivity D-dimer quantitative testing can rule out DVT. For patients with positive results, further vascular ultrasound examination is recommended (Highly recommended).

 D-dimer is used for the exclusion diagnosis of PE. The process is as follows:

Screening for acute PE should be based on clinical experience or clinical possibility (Wells score or modified Geneva score) combined with D-dimer testing. For patients with moderate or low clinical evaluation potential, PE can be excluded if the high-sensitivity D-dimer quantitative test result is negative. If D-dimer is positive, further confirmatory examinations are recommended, such as CT pulmonary angiography (CTPA) (highly recommended).

Disseminated intravascular coagulation (DIC) is a clinical syndrome characterized by bleeding and microcirculatory failure. It is not recommended that D-dimer alone is used for the diagnosis of DIC. It should be evaluated in conjunction with other coagulation indicators and platelet count. Continuous and dynamic monitoring of D-dimer levels in patients with DIC can provide a basis for clinical management (recommended).

Elevated D-dimer levels are the most common feature of COVID 19-related coagulopathy. D-dimer detection has many application values in COVID 19, such as prognostic assessment, VTE risk assessment, and anticoagulation treatment guidance. It is recommended that D-dimer be used as one of the routine screening items for admission of COVID 19 patients. The D-dimer level on admission can help evaluate the severity and prognosis of the disease (highly recommended); it is recommended to regularly monitor the D-dimer levels of hospitalized COVID 19 patients. A significantly elevated D-dimer (if >3000 μg/L) indicates an increased risk of VTE. VTE screening and thromboprophylaxis need to be considered (recommended); for non-critical COVID-19 hospitalized patients with elevated D-dimer and low bleeding risk, therapeutic doses of low molecular weight heparin or unfractionated heparin are better than prophylactic doses (recommended); after COVID 19 hospitalized patients are discharged, those who still have elevated D-dimer should be given a 30-day prophylactic dose of DOAC (such as rivaroxaban) rather than no anticoagulant drugs (recommended).

D-dimer can be used to evaluate the prognosis of patients treated with oral anticoagulants (recommended); D-dimer can be used to determine whether patients with VTE need prolonged anticoagulation and whether anticoagulation needs to be resumed (recommended).

Due to the low elimination efficiency, it is not recommended to routinely use D-dimer to exclude VTE in cancer patients (recommended); D-dimer can be used to assess the risk of VTE in cancer patients in combination with other clinical factors (recommended).