title: The additional value of the CRP test in patients in whom the primary care physician excluded pulmonary embolism.
abstract: BACKGROUND
  After excluding pulmonary embolism (PE) with an unlikely Wells-decision rule and a negative D-dimer test, the general practitioner still has to differentiate between clinically relevant and clinically non-relevant diseases accounting for the presented symptoms. A negative D-dimer test makes clinically relevant disease less likely. The C-reactive protein (CRP) test could be of additional value to make this differentiation.
  
  
  OBJECTIVE
  To assess whether an unlikely Wells-decision rule in combination with a negative point of care D-dimer test not only can safely exclude PE but also, in combination with a negative CRP-test, any other clinically relevant disease.
  
  
  METHODS
  We used data of a prospective study including 598 primary care patients suspected of pulmonary embolism. We included all patients, referred to secondary care for reference testing, with an unlikely Wells-decision rule and a negative point of care D-dimer test. We included 191 patients and imputed the CRP-test results in 60 patients. Alternative diagnoses were divided in clinically relevant diseases and clinically non-relevant diseases. A ROC-curve was constructed to determine the optimal CRP-cut-off.
  
  
  RESULTS
  The optimal CRP cut-off value appeared to be 10 mg/l. A total of 116 patients had a CRP < 10 mg/l of whom 12 patients (10%) had a clinically relevant disease. Two patients (2%) needed hospital admission. A total of 75 patients had a CRP ≥ 10 mg/l of whom 32 patients (43%) had a clinically relevant disease. Fifteen patients (20%) were admitted to hospital.
  
  
  CONCLUSIONS
  The CRP-test is enhancing diagnostic decision making in patients in whom the general practitioner excluded PE.
authors.affiliation: Academic Medical Centre, Department of General Practice , Amsterdam , The Netherlands.
authors.forename: Wim A M
authors.initials: WA
authors.lastname: Lucassen
authors.forename: Marlous
authors.initials: M
authors.lastname: Kuijs-Augustijn
authors.forename: Petra M G
authors.initials: PM
authors.lastname: Erkens
authors.forename: Geert-Jan
authors.initials: GJ
authors.lastname: Geersing
authors.forename: Harry R
authors.initials: HR
authors.lastname: Büller
authors.forename: Henk C P M
authors.initials: HC
authors.lastname: van Weert
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002097:C-Reactive Protein / Q000032:analysis*; D015331:Cohort Studies; D003657:Decision Making; D003937:Diagnosis, Differential; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D058006:General Practice / Q000379:methods; D006801:Humans; D008297:Male; D008875:Middle Aged; D011320:Primary Health Care / Q000379:methods*; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000175:diagnosis*; D012372:ROC Curve; D055815:Young Adult
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D; D002097:C-Reactive Protein