title: Evaluation of D-dimer in the diagnosis of suspected deep-vein thrombosis.
abstract: BACKGROUND
  Several diagnostic strategies using ultrasound imaging, measurement of D-dimer, and assessment of clinical probability of disease have proved safe in patients with suspected deep-vein thrombosis, but they have not been compared in randomized trials.
  
  
  METHODS
  Outpatients presenting with suspected lower-extremity deep-vein thrombosis were potentially eligible. Using a clinical model, physicians evaluated the patients and categorized them as likely or unlikely to have deep-vein thrombosis. The patients were then randomly assigned to undergo ultrasound imaging alone (control group) or to undergo D-dimer testing (D-dimer group) followed by ultrasound imaging unless the D-dimer test was negative and the patient was considered clinically unlikely to have deep-vein thrombosis, in which case ultrasound imaging was not performed.
  
  
  RESULTS
  Five hundred thirty patients were randomly assigned to the control group, and 566 to the D-dimer group. The overall prevalence of deep-vein thrombosis or pulmonary embolism was 15.7 percent. Among patients for whom deep-vein thrombosis had been ruled out by the initial diagnostic strategy, there were two confirmed venous thromboembolic events in the D-dimer group (0.4 percent; 95 percent confidence interval, 0.05 to 1.5 percent) and six events in the control group (1.4 percent; 95 percent confidence interval, 0.5 to 2.9 percent; P=0.16) during three months of follow-up. The use of D-dimer testing resulted in a significant reduction in the use of ultrasonography, from a mean of 1.34 tests per patient in the control group to 0.78 in the D-dimer group (P=0.008). Two hundred eighteen patients (39 percent) in the D-dimer group did not require ultrasound imaging.
  
  
  CONCLUSIONS
  Deep-vein thrombosis can be ruled out in a patient who is judged clinically unlikely to have deep-vein thrombosis and who has a negative D-dimer test. Ultrasound testing can be safely omitted in such patients.
mesh_terms: D000372:Agglutination Tests; D000465:Algorithms; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010690:Phlebography; D011237:Predictive Value of Tests; D015995:Prevalence; D011655:Pulmonary Embolism / Q000175:diagnosis / Q000453:epidemiology; D014463:Ultrasonography; D020246:Venous Thrombosis / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000453:epidemiology
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D