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.

Objectives: 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.

Conclusion: The CRP-test is enhancing diagnostic decision making in patients in whom the general practitioner excluded PE.

Keywords::

• CRP-test
• pulmonary embolism
• D-dimer test
• Wells-decision rule
• sensitivity and specificity

FUNDING

The study was funded by the Dutch Heart Foundation (project number No. 2006B237). The funding source had no role in the design, conduct, or reporting of the study or in the decision to submit the manuscript for publication.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.