Title : Use of blood culture time-to-positivity to significantly reduce laboratory workload
Abstract:
Sepsis has high morbidity and mortality, and continues to be a focus of innovation and improvement internationally. Blood cultures are the single most important microbiological diagnostic tool in the septic patient. Recent guidance produced by NHS England has highlighted the requirement for two sets, four bottles, to be taken if sepsis is suspected. This is in order to increase the sensitivity of isolating the causative agent and guide clinical decision making. This increase in samples sent to the microbiology laboratories as a result of this guidance is substantial and requires careful costing and implementation to accommodate the subsequent increase in work.
To accommodate the increase in workload, it is important to assess workflow and look for ways to decrease waste and make the lab processes lean. One way to prevent unnecessary work for the laboratory, identified through a retrospective audit, is to use set criteria to help identification of blood culture contaminants and stop further unnecessary workup.
It was found that using time to positivity could reproducibly differentiate significant Gram-positive cocci isolates from contaminant isolates. Using these findings, laboratory workup on positive blood culture bottles was adjusted and streamlines. The time to positivity for positive blood culture bottles with Gram-positive cocci only (comprising 51% of total positive samples) was noted. Only those samples that were positive in less than 18 hours received direct antibiotic sensitivity testing (AST) (49% of GPC positive blood cultures). This change resulted in an overall reduction in unnecessary antibiotic susceptibility testing, without impacting patient care. AST was reduced by 26.25% (n=2580) across all positive blood cultures per annum and was estimated to have provided a daily capacity of 70 minutes staff time. This change in practice has reduced cost, reduced workload and had a positive environmental impact.
With increasing pressures on the NHS, it is increasingly important that the workflows in place in the microbiology laboratory are streamlined. Innovations such as this allow for efficient sample processing whilst maintaining quality, to create testing capacity. Shared learning of these innovations across laboratories will greatly advance the service nationally.
