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Am Fam Physician. 2020;101(1):54

Clinical Question

Does knowledge of point-of-care C-reactive protein (CRP) level help physicians avoid prescribing antibiotics without sacrificing benefit in patients with an exacerbation of chronic obstructive pulmonary disease (COPD)?

Bottom Line

CRP guidance, regarding the likelihood that antibiotics will be helpful for patients with acute exacerbation of COPD, safely reduces antibiotic use (number needed to treat = 5). Physicians were advised that antibiotics are unlikely to be helpful if the CRP level is less than 20 mg per L (190.48 nmol per L); that antibiotics may be helpful if the CRP level is 20 to 40 mg per L (190.48 to 380.96 nmol per L), especially in the presence of purulent sputum; and that antibiotics are likely to be helpful if the CRP level is greater than 40 mg per L. (Level of Evidence = 1b–)


CRP is an inflammatory biomarker elevated in patients with pneumonia and bacterial rhinosinusitis, and is recommended by United Kingdom guidelines to help physicians avoid prescribing antibiotics in patients with acute lower respiratory tract infection. These authors wondered if the use of CRP would also be effective in patients with an acute exacerbation of COPD. The researchers recruited 653 patients 40 years and older with documented COPD who were experiencing an exacerbation. The patients were randomized to usual care or care guided by the results of a point-of-care CRP test. The guidance provided was that antibiotics are unlikely to be helpful if the CRP level is less than 20 mg per L, that they may be helpful if the CRP level is 20 to 40 mg per L (especially if the patient also has purulent sputum), and that they are likely to be beneficial if the CRP level is greater than 40 mg per L. They were also told that the decision should be guided by all patient factors, not just CRP level. All patients met at least one of the Anthonisen criteria (increased dyspnea, increased sputum volume, and increased sputum purulence). The mean age of patients was 68 years, 52% were men, and most had Global Initiative on Obstructive Lung Disease stage 2 or 3 severity of their COPD. Patients were telephoned at one and two weeks and were seen in person at four weeks; data on antibiotic use were available for 83%. The primary outcome was antibiotic use, which occurred significantly less often with CRP-guided care (57% vs. 77%; P < .05; number needed to treat = 5). At two weeks, patients in the CRP-guided group had greater improvement in their COPD severity score. The distribution of CRP was as follows: 76% were less than 20 mg per L, 12% were 20 to 40 mg per L, and 12% were greater than 40 mg per L. There were also no differences among groups in other prescriptions, follow-up visits or hospitalizations in the next six months, or the likelihood of pneumonia. The effect of CRP guidance was greater in patients who had more of the Anthonisen criteria and was statistically significant only for those with at least two of the criteria.

Study design: Randomized controlled trial (nonblinded)

Funding source: Government

Allocation: Uncertain

Setting: Outpatient (primary care)

Reference: Butler CC, Gillespie D, White P, et al. C-reactive protein testing to guide antibiotic prescribing for COPD exacerbations. N Engl J Med. 2019;381(2):111–120.

Editor's Note: Dr. Ebell is deputy editor for evidence-based medicine for AFP and cofounder and editor-in-chief of Essential Evidence Plus, published by Wiley-Blackwell. 

POEMs (patient-oriented evidence that matters) are provided by Essential Evidence Plus, a point-of-care clinical decision support system published by Wiley-Blackwell. For more information, see Copyright Wiley-Blackwell. Used with permission.

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