Withholding anticoagulation after a negative computed tomography pulmonary angiogram as a stand‐alone imaging investigation: a prospective management study

BACKGROUND: Accurate diagnosis of pulmonary embolism (PE) is essential and it is not clear whether a computed tomography pulmonary angiogram (CTPA) could be used as a stand-alone imaging investigation. The aim of the study was to test the accuracy of the clinical outcome of a negative CTPA as a stand-alone imaging investigation to exclude PE. METHODS: Five hundred and thirty-four consecutive patients who had a CTPA for diagnosis or exclusion of PE were recruited from March 2003 to October 2004. Four hundred and ninety-four patients had a helical CTPA as a stand-alone imaging investigation for diagnosis or exclusion of PE. A 3-month post-CTPA follow up was carried out in all patients to establish the clinical outcome accuracy of a negative CTPA as a stand-alone imaging investigation. RESULTS: There were 387 (78.3%) negative and 107 (21.7%) positive CTPA examinations. The average age of the patients was 57.16 years (standard deviation 18.57). Among those with a negative CTPA who survived, one patient had deep vein thrombosis and 342 patients had no evidence of an episode of venous thromboembolism or PE at the 3-month follow up. Thirty-eight patients died within the 3-month follow-up period and one patient's death was attributed to suspected PE. The negative predictive value of a CTPA is 99.5% (95% confidence interval 98.1-99.9%). CONCLUSION: Helical negative CTPA examination excludes clinically significant PE as a stand-alone imaging investigation. Where concurrent deep vein thrombosis is suspected, lower limb needs to be imaged by ultrasound if the CTPA is negative.