HOW I DO – DVT – Evaluation for Underlying Cause – PART – 11
HOW I DO – DVT – Evaluation for Underlying Cause – PART – 11
(All the articles published in past are available at www.shyamhemoncclinic.com/blog/)
Question: In last part, we covered some important points related to VTE (Deep Vein Thrombosis and Embolism) 1. More people are dying today from VTE than from Bleeding. 2. Modern lifestyle, obesity, age, cancer, hospitalization, several surgeries, pregnancy are some of the most important risk factors for thrombosis. 3. So many new medicines have come in last two decades i.e. anticoagulants. 4. Symptoms of DVT and how to diagnose using tests. Symptoms and signs are frequently not classical. No blood test can diagnose DVT. 5. Urgency of diagnosis and treatment. Precautions before starting anticoagulation.
Now that we have discussed diagnosis, and work up before starting anticoagulation, can we discuss details of anticoagulation?
Answer: NOT YET. It is important to remember that yes it is urgent to start anticoagulation. But our thought process does not need to end there. In parallel, we have to initiate work up for underlying cause for DVT/VTE. Most commonly, doctors start anticoagulation and then forget to ask the question WHY?
Cause of DVT is either hereditary disorders or acquired. Acquired are far more common. It is important not to miss the most common causes that we discussed i.e. underlying cancer, recent surgery, recent hospitalization, recent immbolization. Obesity is an important risk factor, but we do look for other reasons. Effects of modern lifestyle, obesity, age cannot be detected by a test. Also, see CBC carefully. If there are any signs of myeloproliferative neoplasm e.g. platelets, WBC, or Hb even if mildly on higher side. These changes can be subtle, not always typical very high wbc or very high platelet. They can be just outside of normal range. Or even within normal range, and one may still have minor changes in differential count, or a mild splenomegaly. Molecular tests from blood can then get us to an early diagnosis of MPN.
In addition, age appropriate (means standard recommendations for given age, not for every patient e.g. PSA only if male above age 50, or mammogram only if age above 40) cancer screening is very important. Including at least a USG of abdomen, chest x ray (CT scan if any doubt by history or examination); PSA, stool occult blood for 3 days or colonoscopy, mammogram, PAP smear, low threshold for CT chest if smoker. Even a small asymptomatic cancer can lead to DVT. It does not have to be advanced disease.
Large majority of patients however, do not have a clear underlying reason we can diagnose. Even after extensive blood tests or other tests. When I order detailed thrombophilia panel, I do advise patients that in about 80% cases, we will not find any reason. In western literature, this number is about 50%, largely due to a high number of Factor V Leiden mutation in white population.
Most of the work up can happen in parallel or even weeks later, but what we do need to draw before starting anticoagulation is: lupus anticoagulant. Since this test can be false positive in presence of heparin, LMWH, most oral anticoagulants today. A negative test however is ok even on anticoagulation.
Minimum work up that we order in most patients is: Homocysteine; APLA i.e. lupus anticoagulant, anticardiolipin antibody IgG and IgM, antibeta2 glycoprotein antibody IgG and IgM; blood smear review; USG abdomen, chest x ray; age appropriate cancer screening.
In western literature, homocysteine is considered a very weak risk factor for DVT and guidelines now do not recommend routine testing for this. However, what we and other colleagues have found that in India, homocysteine values are frequently much higher than western datasets. Their high is about 15 or so, whereas here we frequently find over 50 or 75. Likely due to much more common deficiency of vitamin B, but could have additional reasons. Homocysteine is an easy blood test, and if high we can look for deficiency of vitamin B and treat it easily. B1,B6,B12 combination, or simple b complex, or even only B12 & folic acid supplements are used.
Many people routinely order extensive thrombophilia testing, even with first episode of DVT i.e. panels including hereditary factors. Costing about 30-40,000. Remember this is not part of minimum work up we do, as noted above. And why is that? First it is not recommended by guidelines for every patient. Second because it does not change management most of the time. Once which change management are included in minimum work up noted above. Hereditary factors rarely lead to DVT by themselves. Also, most of them are very rare anyways. Hence chance of finding them is very low, and unless patient is very young, or has a strong family history, they should not be routinely tested with first episode of DVT. With second episode, one may consider. There also, it is not mandatory, since in most cases, anticoagulation details are decided by Clinical details of DVT (site, severity, frequency etc), rather than underlying hereditary factors. So for example, if one finds a factor V Leiden mutation with first DVT, duration of anticoagulation does not increase. And if one finds same mutation or absence of it, with second DVT, duration of anticoagulation does not reduce. Same for most other hereditary factors. With second DVT, long term anticoagulation is recommended for most DVT regardless of any such tests. And with first DVT, it is mostly about 6 months, regardless of such tests.
May 11th 2025 Dr Chirag A. Shah; M.D. Oncology/Hematology (USA), 9998084001. Diplomate American Board of Oncology and Hematology. Ahmedabad. drchiragashah@gmail.com www.shyamhemoncclinic.com