Laboratory and clinical impacts of an overnight laboratory service

Delayed initiation of effective antimicrobial therapy for sepsis is associated with increased mortality. Whilst automated blood culture machines operate continuously, this does not align with conventional staff working hours and so turn-around-times (TAT) for reporting gram stains to clinicians are 3-7 times longer for blood cultures that flag positive overnight. We retrospectively compared laboratory TATs and clinical outcomes for blood cultures from 183 patients that flagged positive overnight during a 4-month period before and after the implementation of an overnight laboratory service. Enterobacterales and urinary tract infections were the most frequent pathogens and clinical syndrome respectively, and the prevalence of multi-resistant organisms was 15%. Compared with the pre-implementation period, the post-implementation period was associated with shorter median time from blood culture positivity to gram stain (7.4 vs 1.2 h), first genus level identification (7.2 vs 5.8 h) and first antimicrobial susceptibility result (24.1 vs 7.9 h). Similarly, the median time from blood culture positivity to clinicians first being informed was significantly shorter (9.2 vs 1.3 h). After removal of likely contaminants, 78% of patients were on effective empiric antimicrobials and for patients on ineffective empiric antimicrobials, effective therapy was initiated a median of 3.2 h sooner during the post-implementation period, without impact on mortality. Implementation of an overnight laboratory service was associated with significantly faster TAT for reporting blood culture results and more prompt initiation of effective antimicrobials for patients receiving ineffective empiric therapy, improving attainment of sepsis management goals.