Table 2 Guidance on interpreting C-reactive protein (CRP) results
CRP guidance: | |
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The decision to prescribe antibiotics or not has to be based on a comprehensive assessment of the likely risks and benefits given:  • The patient’s underlying health status (chronic obstructive pulmonary disease (COPD) severity, comorbidities, frailty)  • Clinical features of the current exacerbation | |
Measurement of CRP can aid decision-making but is not meant to replace clinical assessment. Patients with the following features are likely to be at increased risk of complications:  • Severe COPD (GOLD grade III)  • Past history of severe exacerbations (requiring hospitalisation)  • Significant comorbidities (e.g. heart failure, poorly controlled diabetes, lung cancer) | |
Sputum purulence is currently the best clinical predictor of bacterial infection. However:  • Patient-reported sputum colour is generally not reliable  • Purulence can be increased in viral infections as well as bacterial infections  • Try and obtain a sputum sample in order to objectively assess sputum purulence where possible  • Ask the patient how much the colour of their sputum has changed from its usual colour. This is particularly pertinent when it is not possible to objectively assess their sputum | |
CRP measurement: | |
CRP < 20 | Antibiotics are unlikely to be beneficial and usually should not be prescribed |
CRP 20–40 | Antibiotics may be beneficial – mainly if purulent sputum is present. You may decide to prescribe antibiotics after taking into account the patient’s underlying health status and the features of the current exacerbation |
CRP > 40 | Antibiotics are likely to be beneficial. Consider prescribing antibiotics unless the patient is assessed as being at lower risk of complications and unlikely to have a bacterial infection (no increased sputum purulence and no features suggesting severe exacerbation) |