title: D-dimer testing is useful to exclude deep vein thrombosis in elderly outpatients.
abstract: BACKGROUND
  Deep vein thrombosis (DVT) can be safely and reliably excluded in patients with a low clinical probability and a negative D-dimer result but the accuracy and utility of such a strategy is unclear in elderly patients.
  
  
  OBJECTIVE
  We sought to compare the performance of the Wells pretest probability (PTP) model and D-dimer testing between patients of different age groups and to examine the utility of the two PTP model classification schemes (low/moderate/high vs. unlikely/likely) in excluding DVT in elderly outpatients.
  
  
  METHODS
  Pooled analysis of databases from three prospective diagnostic studies evaluating consecutive outpatients with suspected DVT.
  
  
  RESULTS
  A total of 2696 patients were evaluated. DVT was diagnosed in 400 (15%) patients overall and in 50 out of 325 (15.5%) patients > or = 60 years old. The PTP distribution and the prevalence of DVT in each PTP category were similar among the different age groups. The negative predictive values of a low or unlikely PTP score in combination with a negative D-dimer result were 99% for all groups. A negative D-dimer in combination with a low or unlikely PTP excluded 21.7% and 31% of patients > or = 80 years old, respectively.
  
  
  CONCLUSIONS
  The combination of a low or unlikely PTP with a negative D-dimer result can effectively and safely exclude DVT in a significant proportion of elderly outpatients. However, this clinical prediction rule needs to be prospectively validated with different D-dimer assays in this specific population.
authors.affiliation: Thrombosis Program, Division of Hematology, Department of Medicine, University of Ottawa, Ottawa, ON, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Carrier
authors.forename: G
authors.initials: G
authors.lastname: Le Gal
authors.forename: S M
authors.initials: SM
authors.lastname: Bates
authors.forename: D R
authors.initials: DR
authors.lastname: Anderson
authors.forename: P S
authors.initials: PS
authors.lastname: Wells
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D003937:Diagnosis, Differential; D003935:Diagnostic Techniques, Cardiovascular; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D006801:Humans; D011237:Predictive Value of Tests; D011336:Probability; D011446:Prospective Studies; D054556:Venous Thromboembolism / Q000175:diagnosis*
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D