[Thromboembolic events in patients after a negative computed tomography pulmonary angiogram: A retrospective study of...

To determine the value of computed tomography (CT) angiography of the chest as a diagnostic test to exclude pulmonary embolism and to assess compliance with diagnostic protocols for thromboembolic disease.

We retrospectively studied patients who underwent CT angiography of the chest because of suspected pulmonary embolism in 2004. All the patients were followed for 3 months. The percentage of patients diagnosed with a thromboembolic event based on an objective test during the follow-up period was determined. We analyzed the percentage of patients with a negative CT angiogram on whom additional diagnostic tests (ultrasound of the lower limbs and/or ventilation-perfusion lung scintigraphy) were performed.

One hundred sixty-five patients underwent CT angiography of the chest because of suspected pulmonary embolism in 2004. Four of the patients were excluded from the study because they were on chronic anticoagulation therapy and a further 2 were excluded because they had a life expectancy of under 3 months. Of the remaining 159 patients, 60 had CT angiograms that were interpreted as high probability for pulmonary embolism (prevalence of 38%). Thirty-nine of the 99 patients with a negative CT angiogram experienced an objectively confirmed thromboembolic event (63% sensitivity; 95% confidence interval, 53%-73%). Other diagnostic tests were not performed in 46% of the cases.

In our setting, a negative single-detector helical CT angiogram was not sensitive enough to exclude the diagnosis of pulmonary embolism. Furthermore, compliance with internationally accepted diagnostic protocols was far from optimal.