Generally the probability of a thrombus when D-dimer is normal is small, but a thrombus may still be present and further testing is needed to rule out a thrombus.
D-dimer is a degradation product of the body’s fibrin and is an important indicator of thrombosis. When the test is negative, acute or active thrombosis is generally not present, but when thrombus is present in a small blood vessel, the test may be negative due to insensitivity.
A positive D-dimer test result does not confirm the presence of a blood clot in the body. Although the level of D-dimer rises significantly in the presence of a thrombus, a positive test result is only indicative of the possible presence of a thrombus because it is less specific for the diagnosis of thrombosis, and because tumors and infections can also cause D-dimer to rise.
Therefore, D-dimer can only have a certain suggestive effect on thrombosis, and the diagnosis of the existence of thrombus in the body has to rely on angiography and vascular ultrasound and other further examination and joint judgment.