From the Guidelines
D-dimer is a blood test used to detect the presence of blood clots in the body, primarily to rule out deep vein thrombosis (DVT) and pulmonary embolism (PE) in patients with low or moderate clinical probability of these conditions. It measures a protein fragment that appears when a blood clot dissolves in the bloodstream. A negative D-dimer test in these patients reliably excludes thrombosis, avoiding the need for further imaging tests 1. D-dimer is also used to monitor disseminated intravascular coagulation (DIC), a serious clotting disorder. The test works because when clots form, the protein fibrin is created, and when clots break down, fibrin splits into fragments including D-dimer. However, D-dimer has limitations - it can be elevated in many conditions including pregnancy, inflammation, cancer, recent surgery, and advancing age, making it sensitive but not specific 1. A positive result requires additional diagnostic testing to confirm the presence of a blood clot.
Key Points
- D-dimer is used to rule out DVT and PE in patients with low or moderate clinical probability
- A negative D-dimer test reliably excludes thrombosis
- D-dimer is also used to monitor DIC
- The test has limitations, including elevation in various conditions, making it sensitive but not specific
- A positive result requires additional diagnostic testing to confirm the presence of a blood clot
Clinical Use
D-dimer is commonly used in the diagnostic evaluation of patients suspected to have venous thromboembolism (VTE) 1. The high sensitivity fibrin D-dimer assay is the first line of testing for patients with low-to-moderate pretest likelihood of disease. However, the test has limited utility in hospitalized patients and in certain patient populations, such as postsurgical or pregnant patients, due to the high frequency of positive D-dimer results with standard thresholds 1.
Limitations
The D-dimer test has several limitations, including inconsistencies in reporting units and cutoff values 1. The assay should ideally be validated in prospective studies or at least compared with already validated assays. The British Committee for Standards in Haematology guidelines state that testing a minimum of 200 subjects should be done before local approval of a D-dimer assay 1.
Conclusion is not allowed, so the answer will be ended here.
From the Research
D-Dimer Usage
- D-dimer is a diagnostic tool used to measure the levels of a protein fragment produced when a blood clot dissolves [2, 3].
- It is commonly used to help diagnose or rule out thrombotic disorders, such as deep vein thrombosis (DVT) and pulmonary embolism (PE) [4, 5].
Clinical Applications
- D-dimer testing can be used to exclude venous thromboembolism (VTE) in patients with low or intermediate pretest probability [3, 6].
- It can also be used to predict the clinical severity of COVID-19 and to identify patients who may benefit from prolonged anticoagulation [3].
- D-dimer levels can be elevated in several other conditions, such as cancer, renal failure, and pregnancy, which can affect the interpretation of test results [3, 5].
Diagnostic Accuracy
- The diagnostic accuracy of D-dimer testing varies depending on the clinical context and the specific assay used [2, 5].
- D-dimer testing has high sensitivity but low specificity, which can lead to false-positive results [3, 6].
- Adjusting the cutoff values for D-dimer testing based on patient characteristics, such as age and pretest probability, can improve the diagnostic accuracy of the test [3].