Information delay of significant bloodstream isolates and patient mortality: a retrospective analysis of 6,225 adult patients with bloodstream infection

Publication summary

The mortality rate for bloodstream infections globally is estimated to be around 15% to 30%, and quick diagnosis and appropriate treatment are crucial for survival. Much attention has been paid to ensuring that hospitals have access to rapid diagnostic tests for bloodstream infections and sepsis, yet few studies have examined the impact of how quickly a clinician receives diagnostic and susceptibility information and how rapidly or appropriately a clinician reassesses the patient’s care. This study evaluated the association between mortality and delays in reporting blood culture positivity and bacterial species identification in 6,225 patients with bacteremia treated at a Barcelona hospital from January 2013 to December 2019.

Who this is for

• Hospital clinicians, especially intensivists and infectious diseases specialists
• Clinical microbiologists
• Sepsis patient advocacy groups

Key findings

Hospital blood culture reporting process

Blood samples from suspected bacteremia patients were incubated for 5 days, after which positive cultures were gram-stained and bacteria identified via matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).

The large Barcelona-based hospital has infectious diseases clinicians and clinical microbiologists available 24/7, yet during the study period, positive blood culture results were reported immediately to the infectious diseases clinician only during daytime working hours. If a blood culture became positive during nighttime working hours (from 2:00 pm to 8:00 am during 2013–2015, and from 8:00 pm–8:00 am during 2016–2019), it was reported the following morning, leading to a patient reassessment delay of 8 hours or more.

During the study period, 2,130 people had positive results reported immediately (i.e., culture became positive and was identified during daytime hours), and 4,095 people experienced a delay in positive result reporting (i.e., culture became positive and was identified during nighttime hours).

Associations between mortality and microbiology reporting delays

Among 6,225 patients with suspected bacteremia, 625 (10%) died within 30 days, 432 (69.2%) of whom experienced a delay in positive result reporting due to their cultures becoming positive during nighttime hours.

In the initial analysis, delays in reporting had a small association with the risk of 30-day mortality, with an odds ratio (OR) of 1.18. The authors note that the mortality associated with bacteremia decreased starting in 2016, potentially associated with nighttime working hours beginning at 8:00 pm rather than at 2:00 pm.

Enterobacterales reporting delays and risk of death. Fast-growing Enterobacterales were associated with bloodstream infections in 2,867 patients, and delayed reporting occurred in 204 of the 262 of the patients who died from an Enterobacterales bloodstream infection.

When assessing the effects on bacteremia caused by Enterobacterales, the association between information delays and death strengthened significantly (OR: 1.76 in the univariate model). The association between Enterobacterales reporting delays remained strong (OR: 2.22 over 30 days; OR: 2.05 over 14 days; and OR: 1.92 over 7 days) in a multivariate analysis, even when adjusting for other significant risk factors, such as shock and hematological malignancies.

Reporting delays in other bacterial species and risk of death. In the univariate analysis, delays in reporting were associated with small increases in mortality risk (OR: 1.14 for Staphylococcus aureus; OR: 1.14 for Enterococcus species; and OR: 1.05 for Pseudomonas aeruginosa). 

Conclusions and areas for future research

Although access to rapid diagnostics generally means that test results are available quickly, rapid diagnostic testing does not guarantee that results are given to clinicians as soon as they are available or that clinicians will provide immediate patient reassessment and appropriate treatment. The association between delayed microbiology reporting and mortality in critically ill patients may also be stronger than identified in this study for hospitals that do not have 24/7 infectious diseases and clinical microbiology team coverage. Because fast and appropriate care for serious infections is integral, researchers and hospitals must identify pathways for ensuring immediate reporting of positive test results once available in ways that ensure clinicians have the information they need to make life-saving decisions.