title: Performance of age-adjusted D-dimer cut-off to rule out pulmonary embolism.
abstract: BACKGROUND
  Age-adjusted D-dimer cut-off has recently been proposed to increase D-dimer usefulness in older patients suspected of pulmonary embolism (PE).
  
  
  OBJECTIVE
  We externally validated this age-adjusted D-dimer cut-off using different D-dimer assays in a multicenter sample of emergency department patients.
  
  
  METHODS
  Secondary analysis of three prospectively collected databases (two European, one American) of patients suspected of having PE. D-dimer performance for ruling out PE was assessed by calculating negative likelihood ratio (nLR) for D-dimer with age-adjusted D-dimer cut-off (< age × 10 in patients over 50 years) and with conventional cut-off (< 500 μg dL(-1)). Test efficiency was assessed by the number needed to test (NNT) to rule out PE in one patient.
  
  
  RESULTS
  Among 4537 patients included, overall PE prevalence was 10.1%. In the overall population, nLR was 0.06 (95% confidence interval, 0.03-0.09) with conventional cut-off and 0.08 (0.05-0.12) with age-adjusted cut-off. Using age-adjusted cut-off, nLR was 0.08, 0.09 and 0.06 for Vidas(®) , Liatest(®) and MDA(®) assays, respectively. Use of age-adjusted cut-off produced a favorable effect on NNT in the elderly; the greatest decrease was observed in patients > 75 years: NTT halved from 8.1 to 3.6. The proportion of patients over 75 years with normal D-dimer was doubled (27.9% vs. 12.3%).
  
  
  CONCLUSIONS
  Our study shows that age-adjusted D-dimer had low nLR, allowing its use as a rule-out PE strategy in non-high pretest clinical probability patients, as well as using Vidas(®), Liatest(®) or MDA(®) assays. This age-adjusted cut-off increased clinical usefulness of D-dimer in older patients. A large prospective study is required to confirm these results.
authors.affiliation: Emergency Department, Cliniques Universitaires St-Luc, Université Catholique de Louvain, Brussels, Belgium. andrea.penaloza@uclouvain.be
authors.forename: A
authors.initials: A
authors.lastname: Penaloza
authors.forename: P-M
authors.initials: PM
authors.lastname: Roy
authors.forename: J
authors.initials: J
authors.lastname: Kline
authors.forename: F
authors.initials: F
authors.lastname: Verschuren
authors.forename: G
authors.initials: G
authors.lastname: LE Gal
authors.forename: S
authors.initials: S
authors.lastname: Quentin-Georget
authors.forename: N
authors.initials: N
authors.lastname: Delvau
authors.forename: F
authors.initials: F
authors.lastname: Thys
mesh_terms: D000367:Age Factors; D000368:Aged; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011655:Pulmonary Embolism / Q000097:blood*
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D