text: D-dimer testing is of clinical use when there is a suspicion of deep venous thrombosis (DVTl), pulmonary embolism (PE) or disseminated intravascular coagulation (DIC).
  For DVT and PE, there are possible various scoring systems that are used to determine the a priori clinical probability of these diseases; the best-known is the Wells score.
  * For a high score, or pretest probability, a D-dimer will make little difference and anticoagulant therapy will be initiated regardless of test results, and additional testing for DVT or pulmonary embolism may be performed.
  * For a moderate or low score, or pretest probability:
  ** A negative D-dimer test will virtually rule out thromboembolism: the degree to which the D-dimer reduces the probability of thrombotic disease is dependent on the test properties of the specific test used in the clinical setting: most available D-dimer tests with a negative result will reduce the probability of thromboembolic disease to less than 1% if the pretest probability is less than 15-20%. Chest computed tomography (CT angiography) should not be used to evaluate pulmonary embolism for persons with negative results of a D-dimer assay. A low pretest probability is also valuable in ruling out PE.
  ** If the D-dimer reads high, then further testing (ultrasound of the leg veins or lung scintigraphy or CT scanning) is required to confirm the presence of thrombus.  Anticoagulant therapy may be started at this point or withheld until further tests confirm the diagnosis, depending on the clinical situation.
  In some hospitals, they are measured by laboratories after a form is completed showing the probability score and only if the probability score is low or intermediate. This reduces the need for unnecessary tests in those who are high-probability. Performing the D-dimer test first can avoid a significant proportion of imaging tests and is less invasive. Since the D-dimer can exclude the need for imaging, specialty professional organizations recommend that physicians use D-dimer testing as an initial diagnostic.