title: Safety of ruling out acute pulmonary embolism by normal computed tomography pulmonary angiography in patients with an indication for computed tomography: systematic review and meta-analysis.
abstract: BACKGROUND
  Several outcome studies have ruled out acute pulmonary embolism (PE) by normal computed tomography pulmonary angiography (CTPA). We performed a meta-analysis in order to determine the safety of this strategy in a specific group of patients with a strict indication for CTPA, that is, 'likely' or 'high' clinical probability for PE, an elevated D-dimer concentration, or both.
  
  
  METHODS
  Studies that ruled out PE by normal CTPA, with or without subsequent normal bilateral compression ultrasonography (CUS), in patients with a strict indication for CTPA, were searched for in Medline, EMBASE, Web of Science and the Cochrane dataset. The primary endpoint was the occurrence of (fatal) venous thromboembolism (VTE) in a 3-month follow-up period.
  
  
  RESULTS
  Three studies were identified that excluded PE by CTPA alone (2020 patients), and three studies that performed additional CUS of the legs after normal CTPA (1069 patients). The pooled incidence of VTE at 3 months was 1.2% [95% confidence interval (CI) 0.8-1.8] based on a normal CTPA result as a sole test, and 1.1% (95% CI 0.6-2.0) based on normal CTPA and negative CUS findings, resulting in negative predictive values of 98.8% (95% CI 98.2-99.2) and 98.9% (95% CI 98.0-99.4), respectively. This compares favorably with the VTE failure rate after normal pulmonary angiography (1.7%, 95% CI 1.0-2.7). The risk of fatal PE did not differ between the diagnostic strategies (0.6% vs. 0.5%).
  
  
  CONCLUSIONS
  A normal CTPA result alone can safely exclude PE in all patients in whom CTPA is required to rule out this disease. There is no need for additional ultrasonography to rule out VTE in these patients.
authors: Section of Vascular Medicine, Department of General Internal Medicine--Endocrinology, Leiden, The Netherlands.
authors: I C M
authors: IC
authors: Mos
authors: F A
authors: FA
authors: Klok
authors: L J M
authors: LJ
authors: Kroft
authors: A
authors: A
authors: DE Roos
authors: O M
authors: OM
authors: Dekkers
authors: M V
authors: MV
authors: Huisman
mesh_terms: D000792:Angiography / Q000379:methods*; D000925:Anticoagulants / Q000627:therapeutic use; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000096:biosynthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011336:Probability; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000175:diagnosis* / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome; D014463:Ultrasonography / Q000379:methods*; D020246:Venous Thrombosis / Q000097:blood / Q000401:mortality
chemical_list: D000925:Anticoagulants; D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D