title: Risk of deep vein thrombosis following a single negative whole-leg compression ultrasound: a systematic review and meta-analysis.
abstract: BACKGROUND
  In patients with suspected lower extremity deep vein thrombosis (DVT), compression ultrasound (CUS) is typically the initial test to confirm or exclude DVT. Patients with an initial negative CUS result often require repeat CUS after 5 to 7 days. Whole-leg CUS may exclude proximal and distal DVT in a single evaluation.
  
  
  OBJECTIVE
  To determine the risk of venous thromboembolism after withholding anticoagulation in patients with suspected lower extremity DVT following a single negative whole-leg CUS result.
  
  
  METHODS
  MEDLINE, EMBASE, CINAHL, LILACS, Cochrane, and Health Technology Assessments databases were searched for articles published from January 1970 through November 2009. Supplemental searches were performed of Internet resources, reference lists, and by contacting content experts.
  
  
  METHODS
  Included studies were randomized controlled trials and prospective cohort studies of patients with suspected DVT and a negative whole-leg CUS result who did not receive anticoagulant therapy, and were followed up at least 90 days for venous thromboembolism events.
  
  
  METHODS
  Two authors independently reviewed and extracted data regarding a single positive or negative whole-leg CUS result, occurrence of venous thromboembolism during follow-up, and study quality.
  
  
  RESULTS
  Seven studies were included totaling 4731 patients with negative whole-leg CUS examinations who did not receive anticoagulation. Of these, up to 647 patients (13.7%) had active cancer and up to 725 patients (15.3%) recently underwent a major surgery. Most participants were identified from an ambulatory setting. Venous thromboembolism or suspected venous thromboembolism-related death occurred in 34 patients (0.7%), including 11 patients with distal DVT (32.4%); 7 patients with proximal DVT (20.6%); 7 patients with nonfatal pulmonary emboli (20.6%); and 9 patients (26.5%) who died, possibly related to venous thromboembolism. Using a random-effects model with inverse variance weighting, the combined venous thromboembolism event rate at 3 months was 0.57% (95% confidence interval, 0.25%-0.89%).
  
  
  CONCLUSIONS
  Withholding anticoagulation following a single negative whole-leg CUS result was associated with a low risk of venous thromboembolism during 3-month follow-up.
authors.affiliation: Department of Internal Medicine, University of Utah School of Medicine, Salt Lake City, USA.
authors.forename: Stacy A
authors.initials: SA
authors.lastname: Johnson
authors.forename: Scott M
authors.initials: SM
authors.lastname: Stevens
authors.forename: Scott C
authors.initials: SC
authors.lastname: Woller
authors.forename: Erica
authors.initials: E
authors.lastname: Lake
authors.forename: Marco
authors.initials: M
authors.lastname: Donadini
authors.forename: Ji
authors.initials: J
authors.lastname: Cheng
authors.forename: José
authors.initials: J
authors.lastname: Labarère
authors.forename: James D
authors.initials: JD
authors.lastname: Douketis
mesh_terms: D000368:Aged; D000925:Anticoagulants / Q000627:therapeutic use*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011312:Pressure; D016032:Randomized Controlled Trials as Topic; D012306:Risk; D014463:Ultrasonography / Q000379:methods; D020246:Venous Thrombosis / Q000000981:diagnostic imaging* / Q000188:drug therapy* / Q000453:epidemiology
chemical_list: D000925:Anticoagulants