Utility of Blood Cultures in Pneumonia

Abstract

IntroductionBlood cultures are of limited utility in non-severe community-acquired pneumonia, though routinely recommended for severe community-acquired pneumonia or healthcare-associated pneumonia, due to perceived greater bacteremia risk, particularly with multidrug resistant organisms. The utility of this practice is unknown. MethodsIn this observational cohort study, we abstracted data from medical records for consecutive hospitalizations for pneumonia by adults to an academic medical center from 2014-2015. The primary outcomes included bacteremia, multidrug resistant organism bacteremia, and appropriate management changes attributed to culture results, stratified by pneumonia classification (non-severe community-acquired pneumonia, severe community-acquired pneumonia, or healthcare-associated pneumonia) and likelihood the bacteremia was due to pneumonia versus another infection. We assessed the diagnostic test performance of ≥1 guideline-defined risk factors for bacteremia in non-severe community-acquired pneumonia, for whom cultures are routinely recommended. ResultsOf 456 pneumonia hospitalizations, 30 (6.6%) had bacteremia, with a greater incidence in severe community-acquired pneumonia (14.7%) than non-severe communityacquired pneumonia (7.8%) and healthcare-associated pneumonia (6.6%; p=0.12). Seventeen bacteremia cases were likely due to pneumonia (3.7%). Only 2 (0.4%) had multidrug resistant organisms (both healthcare-associated pneumonia), 1 of whom was due to pneumonia. Appropriate management changes occurred in 8 cases (1.8%; 7 deescalation and 1 escalation of antibiotics); only 1 with bacteremia likely due to pneumonia (de-escalation). The one case of appropriate antibiotic escalation occurred in a patient with vancomycin-resistant enterococcus unrelated to pneumonia. Having ≥1 guideline-defined risk factors did not identify bacteremia in non-severe communityacquired pneumonia (positive likelihood ratio, 1.10, 95% CI, 0.61-1.99). ConclusionRoutine blood cultures in pneumonia have extremely low yield and utility irrespective of severity and risk.

Low Yield, High Costs

“…However, their results delineate a manifesto against the routine collection of BC in patients with CAP. Consistent with the findings of previous studies, [2][3][4] the vast majority of BC in patients with CAP yield negative results. In this study 3996 of 4349 patients (91.9%) were reported to have negative BC results.…”

Community-acquired bacterial pneumonia in adults: An update

“…SCAP showed 13.8 per cent positivity while non-SCAP had only 7.9 per cent yield of blood cultures. Only 65 per cent of bacteraemic CAP had organisms that were likely pneumonia related while 35 per cent had bacteria implicated from non-pulmonary source 70 .…”

Diagnosis of Multidrug-Resistant Pathogens of Pneumonia

“…Although the value of obtaining blood cultures for all hospitalized patients with community-acquired pneumonia is debated, two sets of blood cultures that have been obtained before empiric antibiotic administration in patients that have been hospitalized with severe pneumonia may enhance diagnostic yield [ 15 , 16 ]. Most experts agree that the lower respiratory tract should be sampled for culture, and peripheral blood cultures should be obtained for ventilator-associated pneumonia [ 1 , 17 ].…”