A hospital-wide study of the impact of introducing a personal data assistant-augmented blood culture round

Abstract

Blood culture is the cornerstone of an established aetiological diagnosis of septicaemia. The automated blood culture systems used for this purpose have changed little in the last decade, and the clinical value of results depends on a variety of factors, including pre- and post-analytical variables. Growing scepticism over the value of blood culture results and pressure for the introduction of molecular detection systems have prompted a critical path analysis of pre-, peri- and post-analytical stages in the generation of positive blood culture results. The impact of a positive blood culture was studied in a teaching hospital for 12 months before and 12 months after the introduction of a microbiologist's blood culture round. Active culture reporting via a blood culture ward round was supported by a personal data assistant database of contemporaneous laboratory and clinical data. Hospital occupancy and death register records were subsequently obtained through the State Government data linkage project. There was no evidence that faster laboratory generation of positive blood culture results, faster reporting of results or direct clinical interaction with the patient's primary medical team reduced the risk of death in hospital. However, there was a threefold increase in the rate of death in hospital following a 1 day delay in collection of blood cultures after hospital admission (P=0.0010). The overall duration of hospital stay for patients with a positive blood culture fell by 2.5 days compared with the previous 12 month period (P=0.0003). The interval between the initial positive culture result and patient discharge fell by 2 days (P=0.0010). This difference was attributed to shorter overall admissions and shorter intervals between positive cultures containing Gram-positive cocci and subsequent patient discharge (P=0.0018). An increased mortality rate from community-acquired bacteraemic infections was associated with delayed culture collection, but not with a prolonged laboratory processing interval. Thus, the speed of conventional blood culture analysis and the form of clinical reporting have little direct effect on the clinical outcome of bacteraemia, but may contribute to a reduction in the length of hospital admission. Introduction of molecular identification tests, such as multiplex PCR methods, at the Gram-stain stage of blood culture is unlikely to affect the rate of death in hospital, but may reduce the length of hospital admission.