CTPA is enough
Some advocate for additional testing, such as leg ultrasound, even after negative CT pulmonary angiogram (CTPA) in patients with likely pretest probability of PE. This retrospective look at 2522 patients undergoing PE workup found that 845 had "likely" pretest probability based on simplified revised Geneva (dichotomized results as "PE likely" or "PE unlikely") and there was a 30% prevalence of PE in this group; 314 were ruled out for PE with CTPA. All were followed for 3 months; 2 had venous thromboembolism (VTE), making the probability of VTE 0.6%. Technically only 1 had confirmed VTE; the other was "undetermined" after PE workup, but they counted it as PE. It's hard to know if a CT-only approach would also be safe in high pretest probability patients, if the original Geneva score had been used.
Patients with a "PE likely" pretest probability may be considered ruled out for PE after negative CTPA with no additional testing, assuming the same (or lower) prevalence of PE in your setting.
Safety of multidetector computed tomography pulmonary angiography to exclude pulmonary embolism in patients with a likely pretest clinical probability. J Thromb Haemost. 2017 Jun 2. doi: 10.1111/jth.13746. [Epub ahead of print]
Peer reviewed by Thomas Davis.