Computed tomographic venography is specific but not sensitive for diagnosis of acute lower-extremity deep venous thrombosis in patients with suspected pulmonary embolus

Purpose: Duplex ultrasound scanning (US) is the accepted standard means of diagnosis for lower-extremity suprageniculate deep venous thrombosis (LE-DV T). Computed tomographic venography (CTV) has been proposed as an alternati ve modality for diagnosis of LE-DVT in patients with suspected pulmonary em bolism (PE). This study compared CTV with US as a means of diagnosing acute LE-DVT. Methods: A retrospective review of US and CTV scans from 136 patients with suspected PE who underwent both studies to exclude acute LE-DVT at a single institution was performed. Studies were reviewed and coded in a blinded ma nner. US was considered to be the reference test. Direct costs of each stud y were determined by using commercial software. Results: The sensitivity and specificity rates of CTV were 71% and 93%, res pectively. The positive predictive value, negative predictive value, and ac curacy rates of CTV were 53%, 97%, and 90%, respectively. DVT localization was the same in eight of 10 cases in which the results of both US and CTV w ere positive. CTV costs and charges per study were greater than those of US by $46.88 and $602.00, respectively. Conclusion: CTV is specific, but has a lower sensitivity rate and positive predictive value for the diagnosis of acute LE-DVT compared with US. Additi onally, CTV is more costly than US scanning. Because of the lower sensitivi ty rate and positive predictive value and the increased cost of CTV, US rem ains the screening study of choice in cases of suspected acute LE-DVT.