title: D-dimer Interval Likelihood Ratios for Pulmonary Embolism.
abstract: The objective was to estimate D-dimer interval likelihood ratios (iLRs) for diagnosing pulmonary embolism (PE).
  
  
  
  The authors used pooled patient-level data from five PE diagnostic management studies to estimate iLRs for the eight D-dimer intervals with boundaries 250, 500, 750, 1,000, 1,500, 2,500, and 5,000 ng/mL. Logistic regression was used to fit the data so that an interval increase corresponds to increasing the likelihood ratio by a constant factor.
  
  
  
  The iLR for the D-dimer interval 1,000-1,499 ng/mL was essentially 1.0 (0.98 with 95% confidence interval [CI] = 0.82-1.18). In the logistic regression model, the constant between-interval factor was 2.0 (95% CI = 1.9-2.1). Using these iLR estimates, if the pre-D-dimer probability of PE is 15%, only a D-dimer less than 500 ng/mL will result in a posttest probability below 3%; if the pretest probability is 5%, the threshold for a "negative" D-dimer is 1,000 ng/mL.
  
  
  
  A decision strategy based on these approximate iLRs agrees with several published strategies.
authors.affiliation: Department of Epidemiology and Biostatistics, UCSF, San Francisco, CA.|Department of Emergency Medicine, Mills-Peninsula Medical Center, Burlingame, CA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Kohn
authors.affiliation: Department of Medicine-Thrombosis and Hemostasis, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Frederikus A
authors.initials: FA
authors.lastname: Klok
authors.affiliation: Department of Vascular Medicine, Academic Medical Center (NvE), Amsterdam, the Netherlands.
authors.forename: Nick
authors.initials: N
authors.lastname: van Es
mesh_terms: D000465:Algorithms; D015415:Biomarkers / Q000032:analysis; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D006801:Humans; D016015:Logistic Models; D015201:Meta-Analysis as Topic; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000175:diagnosis*; D012680:Sensitivity and Specificity; D013997:Time Factors
chemical_list: D015415:Biomarkers; D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D