Testing CRP level safely reduced antibiotic use in patients with COPD exacerbation

Testing C-reactive protein (CRP) levels in patients with acute exacerbations of chronic obstructive pulmonary disease (COPD) substantially reduced antibiotic use without significantly affecting clinical outcomes, a randomized controlled trial found.

Researchers enrolled patients with COPD who presented to a total of 86 primary care practices in the U.K. with at least one of the Anthonisen criteria for acute exacerbation (e.g., increased dyspnea, increased sputum volume, and increased sputum purulence). A total of 649 patients were randomly assigned to receive usual care guided by point-of-care testing of CRP level (n=325) or usual care alone (n=324). For the intervention group, clinicians were advised to use CRP thresholds to help determine the potential utility of antibiotics: unlikely beneficial (<20 mg/L), likely beneficial (>40 mg/L), and possibly beneficial (between 20 and 40 mg/L, mainly with presence of purulent sputum). However, clinical decision making was not based solely on CRP level. Results were published online on July 11 by the New England Journal of Medicine.

At four weeks, fewer patients in the CRP group reported antibiotic use than in the usual-care group (57.0% vs. 77.4%; adjusted odds ratio, 0.31; 95% CI, 0.20 to 0.47). Antibiotic prescriptions issued during four weeks of follow-up were ascertained for 96.9% of patients. A lower percentage of those in the CRP group than in the usual-care group received an antibiotic prescription (59.1% vs. 79.7%; adjusted odds ratio, 0.30; 95% CI, 0.20 to 0.46). In addition, a lower percentage of patients in the CRP group than in the usual-care group received an antibiotic prescription at the initial visit (47.7% vs. 69.7%; adjusted odds ratio, 0.31; 95% CI, 0.21 to 0.45). The majority of prescriptions were for seven days (138 [87.3%] patients in the CRP group and 185 [79.1%] in the usual-care group).

At two weeks, the adjusted mean difference in total score on the Clinical COPD Questionnaire was −0.19 points (two-sided 90% CI, −0.33 to −0.05) in favor of the CRP group. The published minimal clinically important difference is 0.4, so this result indicated that less antibiotic use did not compromise patient-reported disease-specific quality of life. At six months, health care-seeking behavior and measures of patient well-being did not differ meaningfully between groups.

Study authors noted that patients' awareness of receiving the CRP testing may have contributed to enhanced COPD-related health status. They added that although the primary outcome was patient-reported, this was an attempt to capture actual antibiotic use.

The results are compelling enough to support CRP testing as an adjunctive measure to guide antibiotic prescribing in this patient population, an accompanying editorial said. “Whether primary care practices in the United States would embrace point-of-care CRP testing is another matter, given the regulatory requirements for in-office laboratory testing and uncertainty about reimbursement,” the editorialists wrote.