title: Association between asymptomatic deep vein thrombosis detected by venography and symptomatic venous thromboembolism in patients undergoing elective hip or knee surgery.
abstract: BACKGROUND
  Venography is commonly used to compare the efficacy of different thromboprophylaxis strategies for preventing deep vein thrombosis (DVT) in patients undergoing total hip replacement (THR) or total knee replacement (TKR).
  
  
  METHODS
  We explored the relation between asymptomatic DVT and symptomatic venous thromboembolism (VTE) in patients undergoing THR or TKR treated with standard doses of enoxaparin (30 mg b.i.d. or 40 mg o.d.) by comparing the incidence of asymptomatic DVT in venographic studies with the incidence of symptomatic VTE in studies where venography was not performed.
  
  
  RESULTS
  In 10 venographic studies involving 5796 patients, the incidence of asymptomatic DVT after THR was 13.2% [95% CI, 12.2-14.2%] and after TKR was 38.1% (95% CI, 35.5-40.8%). In two studies involving 3500 patients who did not undergo venography, the 90-day incidence of symptomatic VTE after THR was 2.7% (95% CI, 2.1-3.4%) and after TKR was 1.8% (95% CI, 0.9-2.7%). For every symptomatic VTE in THR studies where venography was not performed there were five asymptomatic DVTs in the venographic studies; for TKR, the ratio was 1:21. The incidence of asymptomatic DVT and the symptomatic VTE/asymptomatic DVT ratio was influenced by the venogram reading committee (Gothenburg vs. Hamilton: total DVT after THR, 19.5% vs. 8.7%, P < 0.0001; for TKR, 42.7% vs. 27.2%, P < 0.0001).
  
  
  CONCLUSIONS
  Comparisons across trials show a consistent relation between asymptomatic venographic DVT in patients undergoing elective THR or TKR surgery and symptomatic VTE in patients not undergoing venography. Differences exist in the strength of the relation depending on the type of surgery and the venogram reading committee.
authors.affiliation: Department of Radiology, King's College Hospital, London, UK.
authors.forename: D J
authors.initials: DJ
authors.lastname: Quinlan
authors.forename: J W
authors.initials: JW
authors.lastname: Eikelboom
authors.forename: O E
authors.initials: OE
authors.lastname: Dahl
authors.forename: B I
authors.initials: BI
authors.lastname: Eriksson
authors.forename: P S
authors.initials: PS
authors.lastname: Sidhu
authors.forename: J
authors.initials: J
authors.lastname: Hirsh
mesh_terms: D000925:Anticoagulants / Q000008:administration & dosage; D002986:Clinical Trials as Topic; D017984:Enoxaparin / Q000008:administration & dosage; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D007720:Knee Prosthesis / Q000009:adverse effects*; D010690:Phlebography; D011183:Postoperative Complications / Q000000981:diagnostic imaging* / Q000209:etiology* / Q000517:prevention & control; D011446:Prospective Studies; D013923:Thromboembolism / Q000000981:diagnostic imaging* / Q000209:etiology* / Q000517:prevention & control; D020246:Venous Thrombosis / Q000000981:diagnostic imaging* / Q000209:etiology* / Q000517:prevention & control
chemical_list: D000925:Anticoagulants; D017984:Enoxaparin