Derivation and validation of a Bayesian network to predict pretest probability of venous thromboembolism

Ann Emerg Med. 2005 Mar;45(3):282-90. doi: 10.1016/j.annemergmed.2004.08.036.


Study objective: A Bayesian network can estimate a numeric pretest probability of venous thromboembolism on the basis of values of clinical variables. We determine the accuracy with which a Bayesian network can identify patients with a low pretest probability of venous thromboembolism, defined as less than or equal to 2%.

Methods: Using commercial software, we derived a population of Bayesian networks from 25 input variables collected on 3,145 emergency department (ED) patients with suspected venous thromboembolism who underwent standardized testing, including pulmonary vascular imaging, and 90-day follow-up (11.0% of patients were venous thromboembolism positive). The best-fit Bayesian network was selected using a genetic algorithm. The selected Bayesian network was tested in a validation population of 1,423 ED patients prospectively evaluated for venous thromboembolism, including 90-day follow-up (8.0% were venous thromboembolism positive). The Bayesian network probability estimate was normalized to a score of 0% to 100%.

Results: Of 1,423 patients in the validation cohort, 711 (50%; 95% confidence interval [CI] 47% to 52%) had a score less than or equal to 2% that predicted a low pretest probability. Of these 711 patients, 700 (98.5%; 95% CI 97.2% to 99.2%) had no venous thromboembolism at follow-up.

Conclusion: A Bayesian network, derived and independently validated in ED populations, identified half of the validation cohort as having a low pretest probability (< or =2%); 98.5% of these patients were correctly classified by the network.

Publication types

  • Validation Study

MeSH terms

  • Adult
  • Aged
  • Algorithms
  • Bayes Theorem
  • Decision Support Techniques*
  • Female
  • Fibrin Fibrinogen Degradation Products / analysis
  • Humans
  • Male
  • Middle Aged
  • Predictive Value of Tests
  • Prospective Studies
  • Pulmonary Embolism / diagnosis
  • Thromboembolism / blood
  • Thromboembolism / diagnosis*
  • Venous Thrombosis / blood
  • Venous Thrombosis / diagnosis*


  • Fibrin Fibrinogen Degradation Products
  • fibrin fragment D