title: A diagnostic strategy involving a quantitative latex D-dimer assay reliably excludes deep venous thrombosis.
abstract: BACKGROUND
  Because clinical diagnosis is inaccurate, objective testing is usually considered necessary when patients present with suspected deep venous thrombosis (DVT).
  
  
  OBJECTIVE
  To determine whether a negative result on a quantitative latex D dimer assay eliminates the need for further investigation in patients with a low or moderate pretest probability of DVT.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  Three tertiary care hospitals in Canada.
  
  
  METHODS
  556 consecutive outpatients with suspected first DVT.
  
  
  METHODS
  Patients were categorized as having a low, moderate, or high pretest probability of DVT and then underwent D-dimer testing. Patients with low or moderate pretest probability and a negative D-dimer result had no further diagnostic testing and received no anticoagulant therapy. Serial compression ultrasonography was performed in all other patients. Patients who did not receive a diagnosis of DVT were followed for symptomatic venous thromboembolism.
  
  
  METHODS
  Objectively confirmed symptomatic venous thromboembolic events during 3 months of follow-up.
  
  
  RESULTS
  283 patients (51%) had low or moderate pretest probability and a negative D-dimer result. One of these patients had DVT during follow-up (negative likelihood ratio, 0.05 [CI, 0.01 to 0.23]). The negative likelihood ratio of the d -dimer test in all patients was 0.03 (CI, 0.01 to 0.16).
  
  
  CONCLUSIONS
  A negative result on a quantitative latex d -dimer assay safely eliminates the need for further testing in patients with low or moderate pretest probability of DVT.
authors.affiliation: McMaster University Medical Centre, HSC 3W11, 1200 Main Street West, Hamilton, Ontario L8N 3Z5, Canada. batesm@mcmaster.ca
authors.forename: Shannon M
authors.initials: SM
authors.lastname: Bates
authors.forename: Clive
authors.initials: C
authors.lastname: Kearon
authors.forename: Mark
authors.initials: M
authors.lastname: Crowther
authors.forename: Lori
authors.initials: L
authors.lastname: Linkins
authors.forename: Martin
authors.initials: M
authors.lastname: O'Donnell
authors.forename: Jim
authors.initials: J
authors.lastname: Douketis
authors.forename: Agnes Y Y
authors.initials: AY
authors.lastname: Lee
authors.forename: Jeffrey I
authors.initials: JI
authors.lastname: Weitz
authors.forename: Marilyn
authors.initials: M
authors.lastname: Johnston
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Ginsberg
mesh_terms: D005338:Fibrin Fibrinogen Degradation Products; D006801:Humans; D007841:Latex Fixation Tests / Q000379:methods*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012307:Risk Factors; D014463:Ultrasonography; D020246:Venous Thrombosis / Q000175:diagnosis* / Q000000981:diagnostic imaging
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D