Likelihood of Bacterial Infection in Patients Treated With Broad-Spectrum IV Antibiotics in the Emergency Department.

OBJECTIVES: Best practice guidelines and quality metrics recommend immediate antibiotic treatment for all patients with suspected sepsis. However, little is known about how many patients given IV antibiotics in the emergency department are ultimately confirmed to have bacterial infection.

DESIGN, SETTING, AND PATIENTS: We performed a retrospective study of adult patients who presented to four Massachusetts emergency departments between June 2015 and June 2018 with suspected serious bacterial infection, defined as blood cultures drawn and broad-spectrum IV antibiotics administered. Structured medical record reviews were performed on a random sample of 300 cases to determine the post hoc likelihood of bacterial infection, categorized as definite, likely, unlikely, or definitely none.

INTERVENTIONS: None.

MEASUREMENTS AND MAIN RESULTS: Among the 300 patients with suspected serious bacterial infections, mean age was 68 years (sd 18), median hospital length of stay was 5 days (interquartile range, 3-8 d), 45 (15%) were admitted directly to ICU, and 14 (5%) died in hospital. Overall, 196 (65%) had definite (n = 115; 38%) or likely (n = 81; 27%) bacterial infection, whereas 104 (35%) were unlikely (n = 55; 18%) or definitely not infected (n = 49; 16%). Antibiotic treatment durations differed by likelihood of infection (median 15 days for definite, 9 for likely, 7 for unlikely, and 3 for definitely not infected). The most frequent post hoc diagnoses in patients with unlikely or definitely no bacterial infection included viral infections (28%), volume overload or cardiac disease (9%), drug effects (9%), and hypovolemia (7%). The likelihoods of infection were similar in the subset of 96 cases in whom emergency department providers explicitly documented possible or suspected sepsis and in the 45 patients admitted from the emergency department to the ICU.

CONCLUSIONS: One third of patients empirically treated with broad-spectrum antibiotics in the emergency department are ultimately diagnosed with noninfectious or viral conditions. These findings underscore the difficulty diagnosing serious infections in the emergency department and have important implications for guidelines and quality measures that compel immediate empiric antibiotics for all patients with possible sepsis.