Pulmonary Embolism Detected by Pulmonary MDCT Angiography in Older Children and Young Adults: Risk Factor Assessment

OBJECTIVE. The purpose of this article is to determine the risk factors for pulmonary embolism (PE) among older children and young adults who underwent pulmonary CT angiography (CTA) for evaluation of clinically suspected PE. MATERIALS AND METHODS. We used our hospital information system to retrospectively identify all consecutive patients 19-25 years old who underwent pulmonary CTA for evaluation of clinically suspected PE between July 2004 and March 2011. Two experienced pediatric radiologists retrospectively and independently reviewed a series of 116 consecutive pulmonary CTA studies from this population. Each examination was reviewed for the presence of PE. Seven possible risk factors (immobilization, prior PE or deep venous thrombosis [DVT], cardiac disease, malignancy, hypercoagulable state, excess estrogen, and central venous line placement) were compared between patients with and without PE using univariate statistics, including Student t test and Pearson chi-square test. Multiple logistic regression modeling was used to identify independent risk factors for PE. Receiver operating characteristic curve analysis was applied to determine the optimal cutoff number of risk factors for predicting a pulmonary CTA result positive for PE. RESULTS. The study population consisted of 116 patients (34 men and 82 women; mean age, 20.7 +/- 1.8 years; range, 18.6-25.4 years) who underwent a total of 116 pulmonary CTA studies. Sixteen (14%) of 116 patients were found to have PE on pulmonary CTA. The level of involvement of PE was segmental in 16 of 31 PEs (52%), lobar in eight (26%), subsegmental in five (16%), and main or central in two (6%). Three risk factors-immobilization (p < 0.001), history of prior PE or DVT (p = 0.001), and cardiac disease (p = 0.004)-were found to be significant independent risk factors for the presence of PE detected by pulmonary CTA. When two or more risk factors were used as the clinical threshold, the sensitivity for positive PE was 75% (12/16 patients) and the specificity was 99% (99/100 patients). CONCLUSION. The use of risk factor assessment as a first-line triage tool has the potential to guide more appropriate use of pulmonary CTA in this population, with potential associated reductions in radiation exposure and costs.