Epidemiological and clinical characteristics of occult bacteremia in an adult emergency department in Spain: influence of blood culture results on changes in initial diagnosis and empiric antibiotic treatment

Epidemiology and Factors Associated With Discharging Patients After Blood Culture Collection in the Emergency Department: A Case-Control Study in Japan

Background

Some patients receive the diagnosis of bloodstream infection (BSI) after discharge from the emergency room (ER). Because the safety of discharging patients after a blood culture collection is unknown, the present study aimed to investigate the prevalence, outcomes, and factors associated with BSI diagnosed after ER discharge.

Methods

This monocentric, case-control study compared patients who received a BSI diagnosis after ER discharge with those who were admitted for BSI. Factors associated with ER discharge after a blood culture collection were identified using multivariate logistic regression analysis.

Results

Between January 2014 and December 2020, 5.5% (142/2575) of patients with BSI visiting the ER were initially discharged. This occurred more commonly during the coronavirus disease 2019 (COVID-19) pandemic in 2020. On multivariate analysis, factors independently associated with the discharge of patients with BSI were the absence of hypotension (adjusted odds ratio [aOR], 15.71 [95% confidence interval {CI}, 3.45–71.63]), absence of altered mental status in the ER (aOR, 8.99 [95% CI, 3.49–23.14]), unknown origin at ER discharge (aOR, 4.60 [95% CI, 2.43–8.72]), and low C-reactive protein (aOR, 3.60 [95% CI, 2.19–5.93]). No difference in 28-day mortality was observed between the groups.

Conclusions

BSI is occasionally diagnosed after ER discharge. The prevalence of BSI diagnosed after ER discharge may have increased during the COVID-19 pandemic. Normal vital signs, unknown origin at ER discharge, and low C-reactive protein were important considerations leading to the discharge of these patients.

Blood cultures of adult patients discharged from the emergency department-is the safety net reliable?

We investigated the clinical implications of the practice in our emergency department (ED) of discharging patients with pending blood cultures. We reviewed the medical records of adults discharged with positive blood cultures from the ED of a 330-bed university hospital during a five-year period. Clinical characteristics, laboratory data, and antibiotic treatment prescribed in the ED and at discharge were accessed. Antimicrobial susceptibility profiles were used to determine whether antibiotic treatment was adequate. The outcomes assessed for 90 days following discharge were return to the ED, hospitalization, modified diagnosis, and death. Of 220,681 visits to the ED, 1362 showed positive blood cultures; of these, 307 (22.5%) were from discharged patients. More than half the isolates (56.3%) were considered contaminants. Of 124 visits with true bacteremia, Enterobacteriaceae were the most common pathogens (67.0%). This is concordant with urinary tract infection (UTI) being the most common diagnosis (52.4%). With antibiotic treatment, 69.4% had been discharged with antibiotic treatment, which was adequate in two-thirds of them. Among the 77 who returned to the ED, 27.5% had persistent bacteremia. The diagnosis was changed in 44.2% of them, mostly with brucellosis or bone and joint infections, and 84.4% were subsequently hospitalized. Within three months, 5.6% of bacteremic patients died, all after hospitalization. Bacteremia in discharged patients occurred mainly in association with UTI. Outcomes were generally favorable, although only about half received appropriate antibiotic treatment. Diagnoses were changed in a relatively high proportion of patients following culture results.

Blood cultures in ambulatory outpatients

Background

Blood cultures are a gold standard specific test for diagnosing many infections. However, the low yield may limit their usefulness, particularly in low-risk populations. This study was conducted to assess the utility of blood cultures drawn from ambulatory outpatients.

Methods

Blood cultures drawn at community-based collection sites in the Calgary Health Region (population 1 million) in 2001 and 2002 were included in this study. These patients were analyzed by linkages to acute care health care databases for utilization of acute care facilities within 2 weeks of blood culture draw.

Results

3102 sets of cultures were drawn from 1732 ambulatory outpatients (annual rate = 89.4 per 100,000 population). Significant isolates were identified from 73 (2.4%) sets of cultures from 51 patients, including Escherichia coli in 18 (35%) and seven (14%) each of Staphylococcus aureus and Streptococcus pneumoniae. Compared to patients with negative cultures, those with positive cultures were older (mean 49.6 vs. 40.1 years, p < 0.01), and more likely to subsequently receive care at a regional emergency department, outpatient antibiotic clinic, or hospital (35/51 vs. 296/1681, p < 0.0001). Of the 331 (19%) patients who received acute care treatment, those with positive cultures presented sooner after community culture draw (median 2 vs. 3 days, p < 0.01) and had longer median treatment duration (6 vs. 2 days, p < 0.01).

Conclusion

Blood cultures drawn in outpatient settings are uncommonly positive, but may define patients for increased intensity of therapy. Strategies to reduce utilization without excluding patients with positive cultures need to be developed for this patient population.