Nov 082019

lab blood testUse of C-reactive protein (CRP) in decision-making may reduce antibiotic use in COPD exacerbations, but not as a replacement for clinical judgment, a study suggested.

Chronic obstructive pulmonary disease (COPD) exacerbations are characterized by increased inflammation in the airways and the body generally. C-reactive protein (CRP) is a serum test for inflammation, and has been explored as a biomarker to help guide treatment in a variety of conditions sharing inflammation as a feature.

Authors randomized 653 patients with acute COPD exacerbations to be managed either through usual care (without access to CRP results) or with a CRP-guided algorithm to determine the use of antibiotics. A point-of-care CRP test was used at all centers, which were loaned by the manufacturer. CRP guided management according to pre-determined cutoff levels:

  • For CRP < 20mg/L, antibiotics were discouraged;
  • CRP 20-40 mg/L, antibiotics considered possibly helpful;
  • For CRP > 40 mg/L, antibiotics were encouraged.

Patients were recruited from primary care practices in the U.K., and asked 2 weeks later how they felt (by standardized questionnaire) and at 2 weeks after that, whether their physician had prescribed them antibiotics at any point throughout the illness.

Those patients randomized to the CRP arm reported receipt of antibiotics less often (57%) than the usual care arm (77%). This differential was driven largely by reductions in antibiotic use among more-symptomatic patients, suggesting the CRP-driven algorithm gave physicians support to withhold antibiotics they normally would have prescribed.

There was no greater observed rate of adverse events in the CRP-driven arm, and the CRP-arm patients reported slightly higher (better) health scores on the COPD questionnaire. Equal numbers of patients were subsequently hospitalized (9%) in each group, and equal numbers were subsequently diagnosed with pneumonia (3-4%).

The study adds to the interesting and growing body of research exploring the role of biomarkers to limit theoretically excessive antibiotic use in patients with COPD exacerbations. Another study published in 2019 showed CRP could help reduce antibiotic use without adverse effects in patients hospitalized with COPD exacerbations, and numerous studies have suggested procalcitonin likewise safely reduces antibiotic use in COPD exacerbations. At least one study suggested using procalcitonin to withhold antibiotics from patients with COPD exacerbations in the ICU could be harmful.

Point-of-care CRP testing was used in the current study, which is not in-house at most physician practices in the U.S. Without widespread adoption of the technology, it’s hard to see how biomarker testing would be integrated into outpatient clinical practice, as the operational delay and inconvenience of lab testing would make it infeasible for the treat-or-not decision made in the office visit.

Many have argued that procalcitonin and CRP aren’t superior to and can't replace clinical judgment, but that may miss the point. In practice, especially in the treatment of hospitalized patients, clinical judgment scarcely factors into the decision to provide antibiotics for COPD exacerbations: they are nearly universally prescribed. Making CRP and/or procalcitonin standard lab tests during hospitalizations for COPD exacerbations would give more physicians the courage and the reminder to appropriately withhold antibiotics or stop them earlier, which (at a cost of $50-$100 per patient for the tests) would probably produce net benefits.

Source: NEJM

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