Comparison of multi-detector CT venography and venous sonography for detecting lower limb deep venous thrombosis in patients with suspected pulmonary embolism
Date of Award
Master of Medicine (MMed)
Imaging and Diagnostic Radiology (East Africa)
Objective: This was a prospective analytic study that aimed to compare the agreement between CT pulmonary angiography (CTPA/CTV) and ultrasonography (US) for diagnosis of thromboembolic disease and determine the sensitivity, specificity, positive and negative predictive values of the 2 tests using the presence of thromboembolic disease as a reference standard.
Methods: 76 consecutive patients who were referred for CTPA at the Radiology department of Aga Khan University Hospital over an 8 month period between December 2008 and July 2009 were included in the study. All the patients underwent combined CTPA/CTV according to the usual departmental protocol. They subsequently had bilateral lower limb duplex US within 24 hours of the CTPA/CTV study. Results for the presence or absence of DVT were analyzed for both CTV and US. Presence of thromboembolic disease was defined by a composite reference standard and this was used to determine the sensitivity, specificity, positive and negative predictive values for both tests.
Results: 73 patients were included in the final analysis. The 2 imaging tests had similar results in 62 (84.93%) patients; CTV was positive and US was negative in 7 (9.6%) patients, while CTV was negative and US was positive in 4 (5.5%) patients. There was a moderate level of agreement (k= 0.528) between CTV and US for detection of DVT. CTV had a much higher sensitivity (94.1%), specificity (100%), PPV (100%), NPV (98.2%) compared to US (58.9%, 94.6%, 76.9%, 88.3% respectively) when the presence of thromboembolic disease was used as a reference standard.
Conclusion: CTV has higher sensitivity, specificity, positive and negative predictive values for detection of asymptomatic DVT compared to US when the presence of venous thromboembolic disease is used as a reference standard. Therefore, in patients suspected to have PE, CTV can be used to detect DVT without an additional duplex US examination.
Wanjohi, R. (2010). Comparison of multi-detector CT venography and venous sonography for detecting lower limb deep venous thrombosis in patients with suspected pulmonary embolism (Unpublished master's dissertation). .