title: Pulmonary embolism: accuracy and safety of a negative CT pulmonary angiogram and value of a negative D-dimer assay to exclude CT pulmonary angiogram-detectable pulmonary embolism.
abstract: This is a retrospective study to determine the accuracy and safety of a negative CT pulmonary angiogram (CTPA) based on clinical outcome and to determine the usefulness of a negative D-dimer assay before CTPA. A total of 483 patients with a negative CTPA study were followed up for 3 months, with the aim of detecting episodes of venous thromboembolism and mortality. Three hundred and forty-nine patients had an immunochromatographic D-dimer assay called 'Simplify', carried out before a CTPA examination. Seventy-eight patients had a negative D-dimer assay and a negative CTPA. Three patients had a negative D-dimer assay and a positive CTPA. All three patients had a moderate pretest clinical probability. Of the 483 patients who had a negative CTPA and a 3-month follow up, 444 (92%) were alive and 39 (8%) had died. Of the 444 patients who were alive, none had any further suspected episode of thromboembolism or had received anticoagulation therapy within the follow-up period. Of those who died, none of the deaths was thought to be as a result of pulmonary embolism (PE). Single-detector helical CT can be used safely as the primary diagnostic test to evaluate PE. Negative Simplify D-dimer assay and low pretest clinical probability exclude CTPA-detectable PE, and a CTPA is unnecessary in this cohort of patients.
authors.affiliation: Department of Radiology, Waikato Clinical School, University of Auckland, Hamilton, New Zealand. rathan67@hotmail.com
authors.forename: R M
authors.initials: RM
authors.lastname: Subramaniam
authors.forename: T
authors.initials: T
authors.lastname: Chou
authors.forename: M
authors.initials: M
authors.lastname: Swarbrick
authors.forename: N
authors.initials: N
authors.lastname: Karalus
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011651:Pulmonary Artery / Q000000981:diagnostic imaging*; D011655:Pulmonary Embolism / Q000097:blood / Q000175:diagnosis* / Q000401:mortality; D015203:Reproducibility of Results; D012189:Retrospective Studies; D036542:Tomography, Spiral Computed / Q000009:adverse effects* / Q000379:methods*
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D