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Blood Cultures Aren't Useful for Managing Immunocompetent CAP Inpatients
Contrary to Medicare "quality measures," blood culture results rarely lead to meaningful changes in therapy for patients with community-acquired pneumonia.
Although 5% to 20% of patients with community-acquired pneumonia (CAP) have positive blood cultures, studies have shown that culture results rarely change antibiotic choices in CAP patients who are started on empirical antibiotics. In another study addressing this issue, these authors retrospectively reviewed medical records of 355 immunocompetent, community-dwelling adults who were admitted for CAP. Patients were included if the attending radiologist reported an infiltrate on the admission chest x-ray and if blood was drawn for at least one set of cultures in the emergency department before administration of antibiotics.
A blood culture was classified as false-positive if the treating physician considered it to be contaminated; all other cultures were classified as true-positive. According to these classifications, 9% of patients had true-positive cultures, and 10% had false-positive cultures. Antibiotic choices were changed in 25 of the 33 cases (76%) with true-positive cultures, most often to drugs with a narrower spectrum of coverage. The culture result was the impetus for the change in 10 cases, and antibiotic resistance was never a reason for changing therapy. Antibiotic therapy was changed in 26 of the 37 cases (70%) with false-positive cultures. Of the 6 cases changed because of the culture result, coverage was broadened in 4 and narrowed in 2.
Comment: This study is not the first to show that blood cultures have limited or no value in guiding treatment of immunocompetent adults admitted for CAP and given empirical antibiotics. Unfortunately, practice quality standards of the Centers for Medicare and Medicaid Services (CMS) require that blood cultures be performed before administering antibiotics in patients who are admitted through the emergency department. The substantial financial waste, additional exposure of staff to infectious material, and potential for misleading results (false-positives) raise serious credibility issues for CMS as it attempts to impose its own definition of "quality." Maybe CMS decision makers should take a peek at the literature.
— Diane M. Birnbaumer, MD, FACEP
Published in Journal Watch Emergency Medicine November 24, 2004
Citation(s):
Corbo J et al. Limited usefulness of initial blood cultures in community acquired pneumonia. Emerg Med J 2004 Jul; 21:446-8.
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