title: Safety of excluding acute pulmonary embolism based on an unlikely clinical probability by the Wells rule and normal D-dimer concentration: a meta-analysis.
abstract: BACKGROUND
  The Wells clinical decision rule (CDR) and D-dimer tests can be used to exclude pulmonary embolism (PE). We performed a meta-analysis to determine the negative predictive value (NPV) of an "unlikely" CDR (<or=4 points) combined with a normal D-dimer test and the safety of withholding anti-coagulants based on these criteria.
  
  
  METHODS
  Prospective studies that withheld anti-coagulant treatment from patients with clinically suspected PE and an "unlikely" CDR in combination with a normal D-dimer concentration without performing further tests were searched for in Medline, Cochrane and Embase. Primary endpoints were the recurrence rate of venous thromboembolism (VTE) and PE-related mortality during 3-months follow-up.
  
  
  RESULTS
  Four studies including 1660 consecutive patients were identified. The pooled incidence of VTE after initial exclusion of acute PE based on an "unlikely" CDR and normal D-dimer was 0.34% (95%CI 0.036-0.96%), resulting in a NPV of 99.7% (95%CI: 99.0-99.9%, random effects-model). The risk for PE related mortality was very low: 1/1660 patients had fatal PE (0.06%, 95%CI 0.0017-0.46%).
  
  
  CONCLUSIONS
  Acute PE can be safely excluded in patients with clinically suspected acute PE who have an "unlikely" probability and a negative D-dimer test and anticoagulant treatment can be withheld. There is no need for additional radiological tests in these patients to rule out PE.
authors: Section of Vascular Medicine, Department of General Internal Medicine - Endocrinology, LUMC, Leiden, The Netherlands.
authors: S M
authors: SM
authors: Pasha
authors: F A
authors: FA
authors: Klok
authors: J D
authors: JD
authors: Snoep
authors: I C M
authors: IC
authors: Mos
authors: R J
authors: RJ
authors: Goekoop
authors: M A
authors: MA
authors: Rodger
authors: M V
authors: MV
authors: Huisman
mesh_terms: D000925:Anticoagulants / Q000627:therapeutic use; D001327:Autoimmune Diseases / Q000150:complications / Q000000981:diagnostic imaging / Q000188:drug therapy; D015415:Biomarkers / Q000097:blood; D002481:Cellulitis / Q000150:complications / Q000000981:diagnostic imaging / Q000188:drug therapy; D003029:Coagulants; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000378:metabolism*; D006801:Humans; D015994:Incidence; D007603:Jurisprudence; D016239:MEDLINE; D008297:Male; D008875:Middle Aged; D011336:Probability; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000097:blood / Q000175:diagnosis* / Q000000981:diagnostic imaging*; D011859:Radiography; D012008:Recurrence; D012449:Safety; D054556:Venous Thromboembolism / Q000097:blood
chemical_list: D000925:Anticoagulants; D015415:Biomarkers; D003029:Coagulants; D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D