title: The predictive characteristics of D-dimer testing in outpatients with suspected venous thromboembolism: a Bayesian approach.
abstract: BACKGROUND
  Despite the widespread use of quantitative methods to measure D-dimer, clinical decisions commonly are based only on binary test information (positive/negative). This study aimed to determine the significance of quantitative D-dimer results in the evaluation of venous thromboembolism (VTE) by means of a differentiated Bayesian approach.
  
  
  METHODS
  Prospective study in 118 outpatients referred for workup of suspected pulmonary embolism (n = 75) or deep vein thrombosis (n = 43). The sensitivity and specificity of D-dimer results obtained by DD VIDAS (Biomerieux, France), STA Liatest (Diagnostica Stago, France), and D-dimer plus (Dade, US) were assessed for five different cut-offs. Further, predictive values and multilevel likelihood ratios were calculated in order to assess the operative test characteristics in excluding or confirming VTE.
  
  
  RESULTS
  At a cut-off of 500 ng/ml and pretest probabilities < 47%, the VIDAS provides a negative predictive value (NPV) > 95%, whereas a positive predictive value (PPV) > 95% is obtained in patients with a D-dimer > 10,000 ng/ml and pretest probabilities > 50%. At a cut-off of 500 ng/ml and pretest probabilities < 33%, the Liatest exhibits a NPV > 95%, whereas a PPV > 95% is obtained in patients with a D-dimer >10,000 ng/ml and pretest probabilities > 37%. Finally, with the D-dimer plus, a NPV > 95% is seen at a cut-off of 150 ng/ml and pretest probabilities < 30%, whereas a PPV > 95% is obtained at a cut-off > 1000 ng/ml and pretest probabilities > 67%.
  
  
  CONCLUSIONS
  D-dimer measurements in outpatients cannot only allow for exclusion but, in some situations, also for confirmation of venous thromboembolism. It is therefore advisable to conduct a quantitative interpretation of D-dimer results.
authors.affiliation: Clinical Decision Making Research Unit, Vorarlberg Institute for Vascular Investigation and Treatment, Feldkirch, Austria.
authors.forename: Lorenz
authors.initials: L
authors.lastname: Risch
authors.forename: Antoinette
authors.initials: A
authors.lastname: Monn
authors.forename: Regina
authors.initials: R
authors.lastname: Lüthy
authors.forename: Hanspeter
authors.initials: H
authors.lastname: Honegger
authors.forename: Andreas R
authors.initials: AR
authors.lastname: Huber
mesh_terms: D000368:Aged; D019540:Area Under Curve; D001499:Bayes Theorem; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D010045:Outpatients; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012372:ROC Curve; D013923:Thromboembolism / Q000097:blood*
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D