CRP in suspected pneumonia

In their latest guideline, CRP is recommended by NICE to help determine if antibiotics are necessary in immunocompetent patients with a pulmonary infiltrate on CXR when it is not clear if this represents pneumonia or not.

There appears to be a reasonable evidence base to support its use, with a CRP > 100 being the trigger for antibiotics. They recommend:

For people presenting with symptoms of lower respiratory tract infection in primary care, consider a point of care C‑reactive protein test if after clinical assessment a diagnosis of pneumonia has not been made and it is not clear whether antibiotics should be prescribed. Use the results of the C‑reactive protein test to guide antibiotic prescribing in people without a clinical diagnosis of pneumonia as follows:

  • Do not routinely offer antibiotic therapy if the C‑reactive protein concentration is less than 20 mg/litre.
  • Consider a delayed antibiotic prescription (a prescription for use at a later date if symptoms worsen) if the C‑reactive protein concentration is between 20 mg/litre and 100 mg/litre.
  • Offer antibiotic therapy if the C‑reactive protein concentration is greater than 100 mg/litre.

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