What are the investigations for Deep Vein Thrombosis (DVT) post-operatively?

From the Guidelines

The investigation of choice for suspected deep vein thrombosis (DVT) is compression ultrasound of the affected limb, as it has high sensitivity and specificity for proximal DVT, with a pooled sensitivity of 94.2% and pooled specificity of 93.8% 1. This non-invasive test should be performed as soon as possible when DVT is suspected. Before ordering imaging, clinicians should assess the patient's pre-test probability using a validated clinical prediction rule such as the Wells score. For patients with low pre-test probability, a negative D-dimer test can safely rule out DVT without further imaging, as DVT is unlikely if the clinical prediction score is low and the D-dimer levels are normal 1. However, D-dimer has limited specificity and is often elevated in hospitalized patients, pregnancy, and older adults. If the D-dimer is positive or the pre-test probability is moderate to high, compression ultrasound should be performed. Some key points to consider when interpreting ultrasound results include:

• The major sonographic criterion is to identify the failure of complete compression of vein walls when pressure is applied to the skin during real-time imaging 1.
• Color-flow Doppler imaging can assist in characterizing a clot as obstructive or partially obstructive 1.
• Using duplex US for the augmentation of venous flow rarely provides additional information when diagnosing DVT, but it can be useful as a secondary diagnostic tool 1. If the initial ultrasound is negative but clinical suspicion remains high, a repeat ultrasound in 5-7 days may be necessary to detect extending calf vein thrombi. In cases where ultrasound is unavailable or inconclusive, alternative imaging modalities include CT venography or MR venography, though these are rarely needed, with MRV having a high sensitivity of 92% for diagnosing DVT 1. Once DVT is diagnosed, baseline complete blood count, renal and liver function tests should be obtained before initiating anticoagulation therapy. It is also important to note that the treatment of choice for DVT is anticoagulation to reduce the risk of DVT extension, recurrent DVT, pulmonary embolism, and post-thrombotic syndrome, with the benefits of anticoagulation therapy in patients with proximal DVT outweighing its risks 1.

From the FDA Drug Label

Table 21: Primary Composite Endpoint and its Components Results * in EINSTEIN CHOICE Study – Full Analysis Set EventXARELTO 10 mg N=1,127 n (%) Acetylsalicylic Acid (Aspirin) 100 mg N=1,131 n (%) XARELTO 10 mg vs Aspirin 100 mg Hazard Ratio (95% CI) * Primary Composite Endpoint13 (1.2)50 (4.4)0.26 (0.14,0.47) p<0. 0001 Symptomatic recurrent DVT8 (0.7)29 (2.6) Symptomatic recurrent PE5 (0.4)19 (1.7) Death (PE)01 (<0.1) Death (PE cannot be excluded)01 (<0. 1)

The answer to the question about investigations for DVT post is not directly addressed in the provided text. Key points are:

• The EINSTEIN CHOICE study compared XARELTO 10 mg to aspirin 100 mg for reduction in the risk of recurrence of DVT and/or PE.
• XARELTO 10 mg was demonstrated to be superior to aspirin 100 mg for the primary composite endpoint of time to first occurrence of recurrent DVT or non-fatal or fatal PE.
• The study results are shown in Table 21. However, the provided text does not directly answer the question about investigations for DVT post. 2

From the Research

Investigations for DVT

Investigations for Deep Vein Thrombosis (DVT) involve a combination of clinical assessment, pre-test probability evaluation, and objective diagnostic testing. The following are key points to consider:

• Clinical assessment: Common symptoms and signs of DVT include pain, swelling, erythema, and dilated veins in the affected limb 3.
• Pre-test probability: Clinical decision rules, such as Wells' score, can be used to stratify DVT into "unlikely" or "likely" categories 3, 4.
• Diagnostic testing:
  • D-dimer test: A normal D-dimer level can exclude DVT, while an increased level requires further testing with compression ultrasound 3, 5, 6.
  • Compression ultrasound: This is the technique of choice for diagnosing lower extremity DVT, as it is non-invasive and easy to administer 5, 6.
  • Other tests: Magnetic resonance venography and venous phase computed axial tomography may also be employed, but are not substitutes for compression ultrasonography as the initial diagnostic test 6.

Diagnostic Algorithms

Diagnostic algorithms for lower extremity DVT typically involve a combination of clinical probability models, D-dimer measurements, and imaging tests. The following are key points to consider:

• Clinical probability models: These help establish the risk of experiencing DVT based on the patient's history and clinical findings 6.
• D-dimer measurements: A negative D-dimer test result can exclude proximal DVT in patients with low pre-test probability 5, 6.
• Imaging tests: Compression ultrasonography is the preferred initial test, with other techniques such as magnetic resonance venography and venous phase computed axial tomography used in special circumstances 6.

Special Circumstances

There are certain special circumstances where the diagnosis of DVT is more problematic, including:

• DVT during pregnancy: Diagnostic algorithms are not as well-established for this population 6.
• Diagnosing rethrombosis: This can be challenging, and requires careful consideration of clinical probability and diagnostic test results 7.
• DVT affecting the upper extremities: Diagnostic algorithms are not as well-established for this population 6.