title: Can an age-adjusted D-dimer level be adopted in managing venous thromboembolism in the emergency department? A retrospective cohort study.
abstract: BACKGROUND
  Patients suspected of having venous thromboembolism (VTE), with a low pretest probability, undergo D-dimer testing. A negative D-dimer, in a low-risk patient rules out VTE with a high degree of certainty because of its high sensitivity. It is, however, a poorly specific test, and the absolute value increases with age. The aim of this study was to establish whether an age-adjusted D-dimer could be safely used instead of a standard cut-off level in low-risk patients over the age of 50 years.
  
  
  METHODS
  This was a retrospective review of 1649 patients with suspected VTE whose D-dimer levels were analysed. In low-risk patients (defined as 'VTE unlikely' using the dichotomized Wells' scores), the outcomes in terms of confirmed VTE diagnosis, hospital admission and investigations using an age-adjusted D-dimer level (measured in D-dimer units) of 5× the age for patients over 50 years of age and 250 ng/ml for patients younger than 50 years of age, was compared with the cut-off standard level (230 ng/ml in all patients).
  
  
  RESULTS
  Of the total group of patients in the VTE unlikely group, the proportion of patients with a negative D-dimer when using the standard cut-off was 64.9% (859/1324). A further 130 patients had a negative D-dimer when the age-adjusted cut-off was used, increasing the proportion of all patients in whom VTE could be excluded without imaging to 74.7% (989/1324).For those patients of 75 years or older, the proportion of patients in whom VTE could be excluded without imaging increased from only 91/242 (37.6%) when using the standard D-dimer cut-off to 154/242 (63.6%) when the age-adjusted cut-off was used.These changes occurred without any additional false-negative findings.
  
  
  CONCLUSIONS
  For patients over the age of 50 years suspected of having VTE with a low pretest probability, increasing the D-dimer cut-off level to 5× the age increases the proportion of patients in whom VTE can safely be excluded without radiological imaging.
authors.affiliation: Department of Emergency Medicine, York Hospital, York, UK.
authors.forename: Tom
authors.initials: T
authors.lastname: Jaconelli
authors.forename: Mazin
authors.initials: M
authors.lastname: Eragat
authors.forename: Steven
authors.initials: S
authors.lastname: Crane
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D015331:Cohort Studies; D003422:Critical Care / Q000379:methods*; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011655:Pulmonary Embolism / Q000097:blood / Q000175:diagnosis / Q000628:therapy*; D012016:Reference Values; D015203:Reproducibility of Results; D012189:Retrospective Studies; D018570:Risk Assessment; D006113:United Kingdom; D054556:Venous Thromboembolism / Q000097:blood / Q000175:diagnosis / Q000628:therapy*; D055815:Young Adult
chemical_list: D015415:Biomarkers; D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D