DDimer for DVT

Measurement of fibrin degradation products (FDPs) in plasma will include fibrinolytic breakdown products of both fibrinogen and cross-linked fibrin. Fibrinogen degradation products are generated in both secondary fibrinolysis (as in DIC) and in primary activation of the fibrinolytic pathway. Cross-linked fibrin degradation products are generated only in secondary fibrinolysis. The D-Dimer test offers a specific measurement of cross-linked fibrin degradation products.

Increased levels of cross-linked fibrin degradation products are found in states of coagulation activation resulting in thrombin formation and subsequent secondary fibrinolysis. Increased levels of D-Dimer have been reported in the following situations: DIC, deep vein thrombosis (DVT), pulmonary embolism, surgery, cancer, and cirrhosis. D-Dimer is a useful test in the work-up of a patient with suspected DIC. The presence of increased D-Dimer levels differentiates DIC from primary fibrinolysis, where the level is not increased.

Several studies have evaluated D-dimer in patients with clinically suspected deep vein thrombosis (DVT) and/or pulmonary embolism (PE). Quantitative D-Dimer assays have a sensitivity of 98.5% and negative predictive value of 95.6% for the diagnosis of proximal DVT (less than 7days) in patients presenting with clinical symptoms of DVT (Am J Clin Pathol, 109:748-753, 1998). It is worth noting that sensitivity was significantly lower for the diagnosis of distal DVT, and specificity of the assay is much lower (35%).

Several words of caution are appropriate.

Firstly, the assay is sensitive for proximal, but not distal DVT's, thus a negative result does exclude the possibility of a distal DVT. Most studies have included only patients with recent (less than 7 days) symptoms of venous thromboembolism, thus the test may not be suitable for exclusion of DVT or PE when the patient has symptoms of longer duration.
Furthermore one should keep in mind that false negative results may occasionally arise, and the level of clinical suspicion must be taken into account when evaluating the test result. No study has yet evaluated the clinical outcome of withholding further testing and anticoagulation in patients with normal D-dimer levels.
Finally, a drawback of all D-dimer methods is low specificity for diagnosis of venous thromboembolism. Causes of false positive results include infection, malignancy, recent surgery and trauma. Thus while a negative result is useful in ruling out venous thromboembolism, a positive result is not useful for confirming the diagnosis.

Predictive Value of D-Dimer for Recurrence of Venous Thromboembolism

The aim of oral anticoagulation after an episode of venous thromboembolism (VTE) is to reduce the risk of recurrent VTE and post-thrombotic syndrome. It is generally accepted that the risk of recurrence is low if a first episode of VTE is associated with a reversible risk factor (such as surgery or immobilization), requiring short-term (3 months) oral anticoagulant therapy (OAT), whereas a longer period of anticoagulation is required if the episode is idiopathic (unprovoked), or if persistent risk factors are present (such as cancer or various thrombophilic defects). The optimal duration of OAT for a first episode of VTE is, however, controversial. The duration of OAT in each patient should be tailored to maximize its preventive benefit and minimize the risk of hemorrhage. A major problem is the absence of reliable markers to predict recurrent thrombosis, which would facilitate selection of patients for longer-term anticoagulation.

Several recent studies suggest that D-dimer levels measured after OAT is discontinued may be useful for predicting the likelihood of recurrent VTE. In one study (Thromb Haemost 2002; 87:7-12) 396 patients with a first episode of VTE had D-dimer assayed on the day OAT was discontinued, and after a further 3-4 weeks, and 3 months. Increased D-dimer was present in 15.5%, 40.3%, and 46.2% of the patients at the three respective time points. D-dimer was persistently elevated in 80 patients, 16.2% of whom developed recurrent VTE, and persistently normal in 127 patients, only 3.9% of whom had a recurrence. The negative predictive value of D-dimer for VTE recurrence was highest for the 3 month value (95.6%). In other words a normal D-dimer value at 3 months after OAT withdrawal was associated with a 95.6% likelihood of no recurrent VTE.

In a subsequent study (Circulation 2003; 108:313-318) 599 patients with a first episode of VTE were tested for D-dimer at one month following OAT withdrawal, and were also screened for inherited thrombophilic defects. Once again, the D-dimer value had a high negative predictive value (94.2%) for VTE recurrence. An elevated D-dimer level one month after OAT discontinuation was associated with an increased risk of recurrent VTE, especially in those with idiopathic VTE (relative risk 2.75), and those with thrombophilic defects such as factor V Leiden (relative risk 5.88).

In summary, patients with a first episode of VTE who have a normal D-dimer level 1-3 months after withdrawal of OAT have a low risk of VTE recurrence. This may help clinicians determine the optimal duration of OAT in individual patients, avoiding unnecessarily prolonged anticoagulation in some. A clinical study is currently underway to evaluate this approach.

Reference range is 0 to 0.4 ug/mL.

Specimen requirement is one 5mL citrate (blue top) tube.




Date Rape Drugs DDimer for DIC DDimer for DVT Dehydroepiandrosterone Dehydroepiandrosterone Sulfate Deoxycorticosteroids Deoxyribonuclease B Ab Dexamethasone Suppression Cushing Syndrome Dexamethasone Suppression Depression Dexamethasone Suppression Test Diabetes Mellitus Diabetes Mellitus Management Differential Leukocyte Count Digoxin Dilute Russel Viper Venom Time Direct Antiglobulin Test Disseminated Intravascular Coagulation DNA Antibody Donath Landsteiner Antibody Drug Induced Thrombocytopenia Drug of Abuse Screen Drugs of Abuse Workplace Testing