C-reactive protein guidance safely reduces antibiotic use in patients with acute exacerbation of COPD (NNT = 5)

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(12):111-120.

Synopsis

CRP is an inflammatory biomarker elevated in patients with pneumonia and bacterial rhinosinusitis, and is recommended by UK guidelines to help physicians avoid 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 CRP is less than 20 mg/L, that they may be helpful if CRP is 20 to 40 mg/L (especially if the patient also has purulent sputum), and that they are likely to be beneficial if CRP is greater than 40 mg/L. They were also told that the decision should be guided by all patient factors, not just CRP. 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 GOLD stage 2 or 3 severity of their COPD. Patients were telephoned at 1 and 2 weeks, and were seen in person at 4 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). In addition, at 2 weeks patients in the CRP-guided group had greater improvement in their COPD severity score. Overall, the distribution of CRP was as follows: 76% less than 20 mg/L, 12% 20 to 40 mg/L, and 12% greater than 40 mg/L. There were also no differences among groups in other prescriptions, follow-up visits or hospitalizations in the next 6 months, or the likelihood of pneumonia. The effect of CRP guidance was greater in patients who had more of the Anthonisen criteria, and was only statistically significant for those with at least 2 of the criteria.