title: Selective D-dimer testing for diagnosis of a first suspected episode of deep venous thrombosis: a randomized trial.
abstract: BACKGROUND
  D-Dimer testing is sensitive but not specific for diagnosing deep venous thrombosis (DVT). Changing the use of testing and the threshold level for a positive test result on the basis of risk for DVT might improve the tradeoff between sensitivity and specificity and reduce the need for testing.
  
  
  OBJECTIVE
  To determine whether using a selective D-dimer testing strategy based on clinical pretest probability (C-PTP) for DVT is safe and reduces diagnostic testing compared with using a single D-dimer threshold for all patients.
  
  
  METHODS
  Randomized, multicenter, controlled trial. Patients were allocated using a central automated system. Ultrasonographers and study adjudicators but not other study personnel were blinded to trial allocation. (ClinicalTrials.gov: NCT00157677)
  
  
  METHODS
  5 Canadian hospitals.
  
  
  METHODS
  Consecutive symptomatic patients with a first episode of suspected DVT.
  
  
  METHODS
  Selective testing (n = 860), defined as D-dimer testing for outpatients with low or moderate C-PTP (DVT excluded at D-dimer levels <1.0 µg/mL [low C-PTP] or <0.5 µg/mL [moderate C-PTP]) and venous ultrasonography without D-dimer testing for outpatients with high C-PTP and inpatients, or uniform testing (n = 863), defined as D-dimer testing for all participants (DVT excluded at D-dimer levels <0.5 µg/mL).
  
  
  METHODS
  The proportion of patients not diagnosed with DVT during initial testing who had symptomatic venous thromboembolism during 3-month follow-up and the proportion of patients undergoing D-dimer testing and ultrasonography.
  
  
  RESULTS
  The incidence of symptomatic venous thromboembolism at 3 months was 0.5% in both study groups (difference, 0.0 percentage point [95% CI, -0.8 to 0.8 percentage points]). Selective testing reduced the proportion of patients who required D-dimer testing by 21.8 percentage points (CI, 19.1 to 24.8 percentage points). It reduced the proportion who required ultrasonography by 7.6 percentage points (CI, 2.9 to 12.2 percentage points) overall and by 21.0 percentage points (CI, 14.2 to 27.6 percentage points) in outpatients with low C-PTP.
  
  
  CONCLUSIONS
  Results may not be generalizable to all D-dimer assays or patients with previous DVT, study personnel were not blinded, and the trial was stopped prematurely.
  
  
  CONCLUSIONS
  A selective D-dimer testing strategy seems as safe as and more efficient than having everyone undergo D-dimer testing when diagnosing a first episode of suspected DVT.
  
  
  BACKGROUND
  Heart and Stroke Foundation of Ontario.
authors: McMaster University, Hamilton, Ontario, Canada. linkinla@mcmaster.ca
authors: Lori-Ann
authors: LA
authors: Linkins
authors: Shannon M
authors: SM
authors: Bates
authors: Eddy
authors: E
authors: Lang
authors: Susan R
authors: SR
authors: Kahn
authors: James D
authors: JD
authors: Douketis
authors: Jim
authors: J
authors: Julian
authors: Sameer
authors: S
authors: Parpia
authors: Peter
authors: P
authors: Gross
authors: Jeffrey I
authors: JI
authors: Weitz
authors: Frederick A
authors: FA
authors: Spencer
authors: Agnes Y Y
authors: AY
authors: Lee
authors: Martin J
authors: MJ
authors: O'Donnell
authors: Mark A
authors: MA
authors: Crowther
authors: Howard H
authors: HH
authors: Chan
authors: Wendy
authors: W
authors: Lim
authors: Sam
authors: S
authors: Schulman
authors: Jeffrey S
authors: JS
authors: Ginsberg
authors: Clive
authors: C
authors: Kearon
mesh_terms: D000293:Adolescent; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D005500:Follow-Up Studies; D006801:Humans; D011336:Probability; D012680:Sensitivity and Specificity; D014463:Ultrasonography; D054556:Venous Thromboembolism / Q000097:blood / Q000175:diagnosis* / Q000000981:diagnostic imaging; D020246:Venous Thrombosis / Q000097:blood / Q000175:diagnosis* / Q000000981:diagnostic imaging
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D