title: Influence of C-reactive protein levels and age on the value of D-dimer in diagnosing pulmonary embolism.
abstract: BACKGROUND
  Recently, the number of performed CT-angiographies to diagnose pulmonary embolism (PE) rised markedly, while the incidence of PE hardly increased. This low yield of CT-angiography leads to more patients exposed to radiation and higher costs.
  
  
  OBJECTIVE
  The diagnostic value of age, C-reactive protein (CRP) and D-dimer in PE was investigated. Additionally an age-adjusted D-dimer cutoff level [age-adjusted cutoff = age/100 mg/L] was compared with the conventional cutoff level in diagnosing PE for patients ≥50 yr.
  
  
  METHODS
  This observational study (2004-2007) included all consecutive patients suspected for PE presenting on the emergency department with a performed CT-angiography after measuring CRP and D-dimer levels.
  
  
  RESULTS
  Of 4609 patients suspected for PE, 1164 patients underwent CT-angiography of whom 309 (26.5%) had PE. Correlation between CRP and D-dimer was 0.42 (P < 0.001). D-dimer and age correlated positively (rs  = 0.33, P < 0.001), but only in patients >50 yr and independent of PE. Multivariate regression analysis showed significant contribution of age, D-dimer and age-adjusted D-dimer for diagnosing PE, but not for CRP. Using an age-adjusted D-dimer cutoff value increased specificity from 37% to 50%, whereas sensitivity declined from 96% to 90%. Applying this age-adjusted cutoff level in patients ≥70 yr, specificity increased from 18% to 40%, while sensitivity decreased from 96% to 88%.
  
  
  CONCLUSIONS
  In the prediction of PE, age and D-dimer levels are relevant, while CRP level is not. Using an age-adjusted D-dimer cutoff in older patients remarkably improves the specificity of D-dimer testing with a minor decline in sensitivity. This may increase the yield of CT-angiography in diagnosing PE.
authors.affiliation: Department of Internal Medicine, Albert Schweitzer Hospital, Dordrecht, the Netherlands; Department of Internal Medicine, Erasmus Medical Center, Rotterdam, the Netherlands.
authors.forename: Meindert Johannes
authors.initials: MJ
authors.lastname: Crop
authors.forename: Claire
authors.initials: C
authors.lastname: Siemes
authors.forename: Paul
authors.initials: P
authors.lastname: Berendes
authors.forename: Frans
authors.initials: F
authors.lastname: van der Straaten
authors.forename: Sten
authors.initials: S
authors.lastname: Willemsen
authors.forename: Mark-David
authors.initials: MD
authors.lastname: Levin
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D002097:C-Reactive Protein / Q000378:metabolism*; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011655:Pulmonary Embolism / Q000097:blood / Q000175:diagnosis* / Q000209:etiology*; D012372:ROC Curve; D012016:Reference Values; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D; D002097:C-Reactive Protein
keywords: C-reactive protein; D-dimer; age-adjusted cutoff; pulmonary embolism; sensitivity; specificity