The duration of treatment for a deep venous thrombosis (DVT) is problematic. Most patients who have one will never have another one, yet those who do have a 5% risk of death due to their recurrent DVT. We need a simple test which separates one group from the other.
This weeks JAMA (no link as issue is not online yet) reports on an article claiming that thrombin generation may be that test. Thrombin is one of the key factors in coagulation and the theory is that patients who generate excess amounts of thrombin are predisposed to developing blood clots. This cohort study showed that patients with peak thrombin generation below 400 nM had a 60% lower risk of developing a recurrent DVT over the course of about 5 years of follow up.
The limiting feature of this study is that they excluded patients with Protein C deficiency, Protein S deficiency and SLE. They also excluded patients with cancer, recent pregnancy, recent trauma, or recent surgery.
That means that before we use this test, we need to make sure that we’ve excluded all of the above diagnoses first. That doesn’t make it such a useful screening test. It would be useful to know is whether patients with Protein C deficiency (as an example) with low thrombin-generation values are at high risk for recurrent DVT. That is, does thrombin-generation trump Protein C deficiency, or vice versa.
What I’d like to have is a test that told me either 1) The patient is low risk or 2) The patient needs further testing. Then, I could do a simple test in all patients with DVT and only send the complicated hypercoagulable workup in patients who had a positive screening test. It seems like thrombin-generation may eventually be that test.
Also in this issue of the journal is a nice quote from Thoreau:
Write while the heat is in you … The writer who postpones the recording of his thoughts uses an iron which has cooled to burn a hole with. He cannot inflame the minds of his audience.
Good advice, which I need to take more often.
Reference: JAMA 2006-07-26 296:4 page 397