From the Guidelines
To evaluate a patient for thrombosis, I recommend starting with a comprehensive clinical assessment including a detailed history of symptoms, risk factors, and physical examination, followed by basic laboratory tests and imaging studies selected based on the suspected location of thrombosis, as this approach allows for prompt initiation of appropriate anticoagulation therapy, reducing the risk of clot propagation and embolization 1. When evaluating a patient for thrombosis, it is essential to consider the following steps:
- Start with a comprehensive clinical assessment including a detailed history of symptoms, risk factors, and physical examination
- Order basic laboratory tests including complete blood count, coagulation profile (PT, PTT, INR), D-dimer, and comprehensive metabolic panel
- Imaging studies should be selected based on the suspected location of thrombosis: duplex ultrasound for deep vein thrombosis in extremities, CT pulmonary angiography for pulmonary embolism, CT or MRI with contrast for cerebral or abdominal vessel thrombosis
- Consider specialized tests for hypercoagulable states including protein C and S levels, antithrombin III, factor V Leiden mutation, prothrombin gene mutation, antiphospholipid antibodies, and homocysteine levels, particularly in patients with unprovoked thrombosis, recurrent events, or family history 1 The diagnostic management of suspected deep vein thrombosis (DVT) should include the combination of pretest probability assessment, D-dimer testing, and (serial) compression ultrasound (CUS) 1. It is also important to note that the threshold for doctors to suspect DVT and initiate diagnostic testing has lowered over the past few years, and this trend is probably attributable to better awareness of the disease, and the availability of non-invasive CUS as an alternative to venography 1. The use of whole-leg US is recommended for the diagnosis of DVT, and if whole-leg US shows only isolated calf vein DVT, treatment is suggested rather than serial testing to rule out proximal extension only in patients with a high pretest probability or if high risk of extension or severe symptoms 1.
From the Research
Thrombosis Workup
- The diagnosis of deep vein thrombosis (DVT) and pulmonary embolism (PE) cannot be made solely on a clinical basis due to the lack of sensitivity and specificity of clinical signs and symptoms 2.
- Non-invasive diagnostic algorithms have been developed that include clinical probability assessment and D-dimer measurement to select patients who require non-invasive imaging 2.
- Compression ultrasonography is used in cases of suspected DVT, while multidetector computed tomography (CT) angiography is used in cases of suspected PE 2.
Diagnostic Characteristics of Lower Limb Venous Compression Ultrasonography
- Lower limb ultrasonography (CUS) has a sensitivity of 41% and specificity of 96% for diagnosing PE 3.
- Proximal CUS has a low sensitivity and cannot be used to rule out PE, but its high specificity allows confirming PE in patients with contraindications to CT angiography 3.
- Whole-leg CUS has a higher sensitivity but low specificity for PE and cannot be recommended 3.
Pulmonary Embolism Diagnosis and Management
- A clinical decision rule can determine the pre-test probability of PE, and if PE is "unlikely", a D-dimer test can be used to exclude PE 4.
- If PE is "likely", chest imaging with computed tomography pulmonary angiogram is accurate and preferred for diagnosing PE 4.
- Ventilation-perfusion (VQ) scan is associated with lower radiation exposure than computed tomography pulmonary angiogram and may be preferred in younger patients and pregnancy 4.
Diagnosis of Deep Venous Thrombosis and Pulmonary Embolism
- Well-validated clinical prediction rules are available to determine the pretest probability of DVT and pulmonary embolism 5.
- A negative D-dimer assay result excludes DVT and pulmonary embolism in patients with low pretest probability 5.
- Multidetector computed tomography angiography is the diagnostic test of choice for pulmonary embolism when the technology is available and appropriate for the patient 5.
Computed Tomography Pulmonary Angiography
- Computed tomography pulmonary angiography (CTPA) has a high sensitivity and specificity for the diagnosis of pulmonary embolism 6.
- CTPA is the imaging test of first choice, and the presence or absence of pulmonary embolism can be determined with sufficient certainty without the need for additional imaging tests after a negative CTPA 6.