An Audit of Blood Cultures in an Emergency Department at a Johannesburg Academic Hospital

Abstract

Background: Blood cultures (BCs) are the standard test for detecting bacteraemia but have come under scrutiny on their usefulness in the Emergency Departments (EDs) as they have a low yield, tend not to alter patient management and may be subject to high contamination rates especially in resource-limited settings. Identifying patients most at risk of bacteraemia may improve BCs’ usefulness. Methods: We conducted a retrospective observational, descriptive and comparative study. Reports from all BCs performed in the ED at Helen Joseph Hospital in 2017 were requested from the National Health Laboratory Service. Data from all positive BCs were used to audit cultured organisms and their sensitivity and resistance patterns. Second, clinical and laboratory data from 206 consecutively selected patients (103 positive and 103 negative BC results) were used to calculate the Shapiro score and the Systemic Inflammatory Response Syndrome (SIRS) criteria as screening tools for sepsis. Results: There was a total of 4011 BCs performed in 2017 of which 715 (17.8%) were positive. Pathogens were cultured in 400 (10.0%) of cases and 315 (7.9%) cultured known contaminants. A positive Shapiro score and SIRS criteria increased the likelihood of a positive BC by 5.6 and 2.3 times, respectively. Positive HIV status, rigors, pulse rate > 115 bpm, deranged mentation, white cells > 18 × 109 cells/L and creatinine > 177 μmol/L were risk factors for positive BCs. Conclusion: There was a low yield of positive BCs from the ED, and using the SIRS criteria or the Shapiro score improves the pre-test probability of positive BC results in patients with suspected sepsis.