Blood cultures in adult patients released from an urban emergency department: a 15-month experience

Abstract

Objective: To determine the frequency of positive blood cultures obtained from adult patients with potential occult bacteremia released from an urban ED and how often these positive cultures alter the subsequent patient course or management.

Methods: This retrospective case series study was conducted at the ED of a large, urban teaching hospital. The study population consisted of a convenience sample of adult patients who presented to the ED with evidence of fever or other clinical conditions suggesting the possibility of bacteremia. The records of all patients who had blood cultures done and who were not admitted to an inpatient service were reviewed. Follow-up was obtained for all patients for whom culture results were positive. A substantial influence on the medical management or clinical course by a (noncontaminant) positive blood culture result was defined as a positive result that directly led to: further diagnostic testing, hospital admission, initiation or alteration of antibiotic therapy, or a different diagnosis. Culture-positive patients who were noncompliant with requested ED follow-up were included in this estimate. An estimate of the laboratory charges per diagnosis of bacteremia also was derived.

Results: Only 24 of 1,350 patients (1.8% of the study population; 95% CI 1.1-2.5%) had true-positive blood cultures. Only 7 patients (0.52% of the population; 95% CI 0.14-0.90%) potentially had their medical management affected by the positive blood culture results. Based on the laboratory charges associated with all blood cultures for this patient group, the cost per clinically significant positive blood culture result was $ 11,570.

Conclusions: The prevalence of bacteremia was 1.8% among the released patients who had blood cultures obtained in the ED. Furthermore, only 0.52% of the patients had positive blood cultures that potentially affected their medical management. Further study is warranted to identify specific criteria for selecting ambulatory patients for whom the use of blood cultures may be cost-effective.