D-Dimer Tests do not Appear Useful for Detecting Deep Vein Thrombosis (DVT)

Past Studies

Past Studies show that individuals with traumatic brain injury are at an increased risk to develop deep vein thrombosis (DVT) following their injuries, especially if their body is motionless or if they have blood flow complications or leg injuries. A DVT is a disorder that occurs when blood-clotting substances form together inside deep veins. These clotting formations can block or stop the flow of blood. They can also move and cause a blockage in a lung artery, termed a pulmonary embolism (PE), which can be life threatening. Early detection is important for the treatment of DVTs.Because of the serious consequences of DVT, routine screening is recommended for individuals with traumatic brain injury in inpatient rehabilitation. Traditionally, Doppler ultrasound, which uses sound waves to detect structures, has been a reliable, but expensive way to identify DVT. It has been suggested that using D-dimer tests to screen for DVT would be more cost-effective. D-dimer testing measures the amount of D-dimer in blood plasma. Plasma D-dimers are produced in the process that occurs when blood forms clots. If D-dimer levels in the blood are elevated, it suggests the presence of the blood clotting process within the body. D-dimer tests are considered to be good, but not perfectly accurate. Past studies suggest that D-dimer testing for individuals with traumatic brain injuries may be useful, although this has not been widely researched. 

This Study

This Study included 35 individuals with severe traumatic brain injuries and no history of DVT treatment. They received care at one TBI Model Systems facility over a three-year period. All of the participants’ legs were treated with intermittent air compressive devices, which use pump-like motions to increase circulation and prevent DVTs. The individuals were screened for DVT at 2, 4, 6, and 8 weeks after their injuries with two different D-dimer testing methods, called the LIA D-line and the ELISA Asserchrom. At the two-week mark, the participants also received Doppler ultrasound screening for DVT. The researchers compared the results and statistically analyzed the data. The researchers found that at two-weeks after the individuals’ brain injuries, none of them had DVTs when tested with the Doppler ultrasound, so evaluation of the D-dimers as predictors of DVTs was not possible. However, even in the absence of DVTs in the legs, most of the participants had elevated scores on the two D-dimer tests indicative, by the test scoring standards, of possible blood clotting. Furthermore, the majority of the participants maintained elevated levels of D-dimer at 4 to 6 weeks. At 8 weeks, 12 participants still showed positive levels of D-dimer. The scores between the two D-dimer tests, the LIA D-Line and the ELISA Asserchrom, produced similar scores—both indicated the possibility of blood clotting. The researchers believe that the scoring standards for both tests are not applicable for detecting blood clots in individuals with traumatic brain injuries. The scoring standards for both tests were determined by analysis of individuals with diagnoses other than traumatic brain injury. 

Who May Be Affected By These Findings

Individuals with traumatic brain injuries, healthcare providers, and researchers

Caveats

This study produced surprising and unexpected results. The researchers are puzzled as to why the D-dimer levels in the individuals with traumatic brain injuries in this study were elevated when DVTs in the legs were not present. The researchers suspect that other biochemical or medical factors may cause the elevated levels, which warrants further research.

Bottom Line

The two D-Dimer tests used in this study did not appear to be useful for detecting deep vein thrombosis (DVT) for individuals with recent traumatic brain injuries. Further, the scoring standards for these two tests did not appear to be applicable for individuals with traumatic brain injuries.

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