Key Points
ÎDeep vein thrombosis (DVT) is a common condition that affects approximately one in 1,000 persons per year.
ÎObjective testing for DVT is crucial because clinical assessment alone is unreliable, and the consequences of misdiagnosis are serious, including fatal pulmonary embolism (PE). Although anticoagulant therapy is effective, its use entails expense, inconvenience, and risk of major hemorrhage.
ÎOnly a minority of patients evaluated for suspected DVT actually have the disease. Therefore, diagnostic strategies must be able to correctly rule in DVT when it is present and safely rule out DVT when it is absent.
ÎThree categories of tests are typically used to determine the probability of DVT:
• Clinical probability assessment based on patient history and clinical findings (See Table 1)
• D-dimer assays • Imaging studies (most commonly venous ultrasonography [US] and less frequently venography, computed tomography [CT], or magnetic resonance imaging [MRI])
ÎDiagnostic testing often requires that the results of more than one assessment are combined. The goal of choosing one strategy over another is to improve patient outcomes in the most efficient manner.
ÎThe strategies in this pocketcard apply to symptomatic ambulatory patients.
Diagnosis Suspected First Lower Extremity (LE) DVT
ÎThe choice of diagnostic tests should be guided by the clinical assessment of pretest probability (PTP, Table 1) rather than by performing the same diagnostic tests in all patients (2-B).
ÎRegardless of PTP, do NOT routinely use CT venography or MRI (1-C).
However, if US is nondiagnostic or impractical (eg, when leg casting or excessive subcutaneous tissue or fluid prevent adequate assessment of compressibility), CT scan venography, MR venography, or MR direct thrombus imaging could be used as an alternative to venography.
ÎIn patients with a low or moderate PTP, initial testing with US would be preferred if the patient has a comorbid condition associated with elevated D-dimer levels and is likely to have a positive D-dimer result, even if DVT is absent.
