Rapid thrombelastography screening for thrombosis risk


Rapid thrombelastography could be used to screen those at risk for thromboembolic events, according to a study presented at the annual meeting of the Central Surgical Association, Chicago, USA.

Jeffry Kashuk of the Rocky Mountain Regional Trauma Center at Denver Health Medical Center presented data from a retrospective pilot study, in which the point-of-care test was found to have detected a hypercoagulable state in patients who went on to develop thromboembolic complications, despite receiving chemoprophylaxis.

“Although chemoprophylaxis for prevention of thromboembolic complications has become standard surgical practice, current evidence suggests that arterial as well as venous thromboses continue to occur with increasing frequency annually,” said Kashuk. “And the number of additional undetected events remains unknown given the variable use of screening techniques.”

“The current plasma assays of blood coagulation are really static,” he said, “and their accuracy is limited due to the addition of buffers. Hence, they remain poor assays of clotting strength in whole blood.

“Thrombelastography, on the other hand, provides a comprehensive evaluation of the viscoelastic properties of blood and allows us to generate a complete analysis of the clotting mechanisms from thrombin activation to fibrinolysis.”

In a seven-month period, rapid thrombelastography identified hypercoagulable states in 57% of 152 patients who were hospitalised for more than 72 hours after surgery. G-values, representing the strength of the clot, greater than 12.4 dynes/cm2 were defined as hypercoagulable, whereas those between 5.3 and 12.4 dynes/cm2 were considered “normal”.

Hypercoagulable patients had a mean G-value of 18 dynes/cm2, whereas the patients with normal coagulability had a mean G-value of 8.6 dynes/cm2. Patients already receiving anticoagulation therapy for established thromboembolic events were excluded, as were those who had blunt carotid/vertebral injuries.

More than 80% of the patients in the study received chemoprophylaxis either with low-molecular-weight heparin or unfractionated heparin. Even so, 19% of the hypercoagulable patients still experienced a thromboembolic event, compared with none of the patients who had normal coagulability. The events were confirmed with duplex ultrasound imaging, computed tomography angiography, or pathologic diagnosis.

In a multivariate analysis, researchers found that, after adjusting for the receipt of chemoprophylaxis, an elevated G-value significantly increased the odds of a thromboembolic event such that every 1 dyne/cm2 increase in G-value raised the risk by 25%.

Kashuk and his colleagues at the Denver Health Medical Center have initiated a randomised trial to evaluate the use of rapid thrombelastography as a screening test.