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Primary Care

Diagnostic value of C reactive protein in infections of the lower respiratory tract: systematic review

BMJ 2005; 331 doi: (Published 30 June 2005) Cite this as: BMJ 2005;331:26
  1. Victor van der Meer (V.van_der_Meer{at}, junior researcher, Department of Medical Decision Making1,
  2. Arie Knuistingh Neven, senior researcher, Department of General Practice and Nursing Home Medicine1,
  3. Peterhans J van den Broek, professor, Department of Infectious Diseases1,
  4. Willem J J Assendelft, professor, Department of General Practice and Nursing Home Medicine1
  1. 1 Leiden University Medical Center, Albinusdreef 2, PO Box 9600, 2300 RC, Leiden, Netherlands
  1. Correspondence to: V van der Meer
  • Accepted 20 April 2005


Objectives To evaluate the diagnostic accuracy of C reactive protein in detecting radiologically proved pneumonia and to evaluate how well it can discriminate between bacterial and viral infections of the lower respiratory tract.

Data sources Medline and Embase (January 1966 to April 2004), with reference checking.

Study selection We included articles comparing C reactive protein with a chest radiograph or with microbiological work-up as a reference test. Two authors independently assessed methodological items.

Results None of the studies met all validity criteria. Six studies used an infiltrate on chest radiograph as reference test. Sensitivities ranged from 10% to 98%, specificities from 44% to 99%. For adults, the relation of C reactive protein with an infiltrate (in a subgroup analysis of five studies) showed an area under the curve of 0.80 (95% confidence interval 0.75 to 0.85). In 12 studies, the relation of C reactive protein with a bacterial aetiology of infection of the lower respiratory tract was studied. Sensitivities ranged from 8% to 99%, specificities from 27% to 95%. These data were epidemiologically and statistically heterogeneous, so overall outcomes could not be calculated.

Conclusion Testing for C reactive protein is neither sufficiently sensitive to rule out nor sufficiently specific to rule in an infiltrate on chest radiograph and bacterial aetiology of lower respiratory tract infection. The methodological quality of the diagnostic studies is generally poor. The evidence not consistently and sufficiently supports a wide introduction of C reactive protein as a rapid test to guide antibiotics prescription.


  • Contributors VvdM collected data, performed the analysis and wrote the manuscript. AKN performed the analysis and revised the paper. PJvdB extensively revised the paper. WJJA conceived the study and extensively revised the paper. VvdM and WJJA are guarantors.

  • Funding None.

  • Competing interests None declared.

  • Ethical approval Not required.

  • Accepted 20 April 2005
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