title: Potential of an age adjusted D-dimer cut-off value to improve the exclusion of pulmonary embolism in older patients: a retrospective analysis of three large cohorts.
abstract: OBJECTIVE
  In older patients, the the D-dimer test for pulmonary embolism has reduced specificity and is therefore less useful. In this study a new, age dependent cut-off value for the test was devised and its usefulness with older patients assessed.
  
  
  METHODS
  Retrospective multicentre cohort study.
  
  
  METHODS
  General and teaching hospitals in Belgium, France, the Netherlands, and Switzerland. Patients 5132 consecutive patients with clinically suspected pulmonary embolism.
  
  
  METHODS
  Development of a new D-dimer cut-off point in patients aged >50 years in a derivation set (data from two multicentre cohort studies), based on receiver operating characteristics (ROC) curves. This cut-off value was then validated with two independent validation datasets.
  
  
  METHODS
  The proportion of patients in the validation cohorts with a negative D-dimer test, the proportion in whom pulmonary embolism could be excluded, and the false negative rates.
  
  
  RESULTS
  The new D-dimer cut-off value was defined as (patient's agex10) microg/l in patients aged >50. In 1331 patients in the derivation set with an "unlikely" score from clinical probability assessment, pulmonary embolism could be excluded in 42% with the new cut-off value versus 36% with the old cut-off value (<500 microg/l). In the two validation sets, the increase in the proportion of patients with a D-dimer below the new cut-off value compared with the old value was 5% and 6%. This absolute increase was largest among patients aged >70 years, ranging from 13% to 16% in the three datasets. The failure rates (all ages) were 0.2% (95% CI 0% to 1.0%) in the derivation set and 0.6% (0.3% to 1.3%) and 0.3% (0.1% to 1.1%) in the two validation sets.
  
  
  CONCLUSIONS
  The age adjusted D-dimer cut-off point, combined with clinical probability, greatly increased the proportion of older patients in whom pulmonary embolism could be safely excluded.
authors.affiliation: Department of Vascular Medicine, Academic Medical Centre, Meibergdreef 9, 1105 AZ, Amsterdam, Netherlands. R.A.Douma@amc.uva.nl
authors.forename: Renée A
authors.initials: RA
authors.lastname: Douma
authors.forename: Grégoire
authors.initials: G
authors.lastname: le Gal
authors.forename: Maaike
authors.initials: M
authors.lastname: Söhne
authors.forename: Marc
authors.initials: M
authors.lastname: Righini
authors.forename: Pieter W
authors.initials: PW
authors.lastname: Kamphuisen
authors.forename: Arnaud
authors.initials: A
authors.lastname: Perrier
authors.forename: Marieke J H A
authors.initials: MJ
authors.lastname: Kruip
authors.forename: Henri
authors.initials: H
authors.lastname: Bounameaux
authors.forename: Harry R
authors.initials: HR
authors.lastname: Büller
authors.forename: Pierre-Marie
authors.initials: PM
authors.lastname: Roy
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011655:Pulmonary Embolism / Q000175:diagnosis*; D012372:ROC Curve; D012015:Reference Standards; D012189:Retrospective Studies
chemical_list: D015415:Biomarkers; D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D