title: Exclusion of pulmonary embolism using C-reactive protein and D-dimer. A prospective comparison.
abstract: Our goal was to evaluate the diagnostic utility of C-reactive protein (CRP) alone or combined with clinical probability assessment in patients with suspected pulmonary embolism (PE), and to compare its performance to a D-dimer assay. We conducted a prospective study in which we performed a common immuno-turbidimetric CRP test and a rapid enzyme-linked immunosorbent assay (ELISA) D-dimer test in 259 consecutive outpatients with suspected PE at the emergency department of a teaching hospital. We assessed clinical probability of PE by a validated prediction rule overridden by clinical judgment. Patients with D-dimer levels > or = 500 microg/l underwent a work-up consisting of lower-limb venous ultrasound, spiral computerized tomography, ventilation-perfusion scan, or pulmonary angiography. Patients were followed up for three months. Seventy-seven (30%) of the patients had PE. The CRP alone had a sensitivity of 84% (95% confidence interval [CI).: 74 to 92%) and a negative predictive value (NPV) of 87% (95% CI: 78 to 93%) at a cutpoint of 5 mg/l. Overall, 61 (24%) patients with a low clinical probability of PE had a CRP < 5 mg/l. Due to the low prevalence of PE (9%) in this subgroup, the NPV increased to 97% (95% CI: 89 to 100%). The D-dimer (cutpoint 500 micro g/l) showed a sensitivity of 100% (95% CI: 95 to 100%) and a NPV of 100% (95% CI: 94 to 100%) irrespective of clinical probability and accurately rule out PE in 56 (22%) patients. Standard CRP tests alone or combined with clinical probability assessment cannot safely exclude PE.
authors.affiliation: Department of Medicine, University Hospital of Lausanne, Switzerland. drahomir.aujesky@verizon.net
authors.forename: Drahomir
authors.initials: D
authors.lastname: Aujesky
authors.forename: Daniel
authors.initials: D
authors.lastname: Hayoz
authors.forename: Bertrand
authors.initials: B
authors.lastname: Yersin
authors.forename: Arnaud
authors.initials: A
authors.lastname: Perrier
authors.forename: Ghassan
authors.initials: G
authors.lastname: Barghouth
authors.forename: Pierre
authors.initials: P
authors.lastname: Schnyder
authors.forename: Angelika
authors.initials: A
authors.lastname: Bischof-Delaloye
authors.forename: Jacques
authors.initials: J
authors.lastname: Cornuz
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D000792:Angiography; D002097:C-Reactive Protein / Q000032:analysis*; D003937:Diagnosis, Differential; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D006801:Humans; D007118:Immunoassay; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000175:diagnosis*; D012680:Sensitivity and Specificity; D036542:Tomography, Spiral Computed; D014463:Ultrasonography; D014692:Ventilation-Perfusion Ratio
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D; D002097:C-Reactive Protein