In the era of the 24 h laboratory, does communicating Gram stain results from blood cultures flagging positive outside of conventional working hours alter patient management?

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.

A prospective study on the effect of time-shifted telephone reporting of blood culture microscopy

Even though dealing with septic patients, the communication of the Gram stain result of positive blood cultures is postponed in most laboratories outside of conventional working hours. There is little evidence from clinics that this issue is being addressed. This study evaluates the potential benefit of an around-the-clock communication. Therefore, the effect of the communication on the antibiotic treatment and the delay of the communication during our non-office hours were measured. Over a three-month period, all blood cultures which were positive for the first time outside the normal working hours were analyzed. Two standardized telephone calls were used to compare the antibiotic treatment before and after the communication of the Gram stain result. The evaluation of the antibiotic treatment was based on the final testing result. In total, 135 patients were included. The rate of the adequate antibiotic increased by 8 percentage points to 69%. The average delay in the patients adjusted to an adequate treatment was 8:57 h (range 2:16-16:59). This prospective study shows a benefit of the immediate communication. Nevertheless, this benefit seems to be partly the result of suboptimal adherence to the guidelines regarding empirical antibiotic treatment. This prospective study has been registered in the German Clinical Trials Register under the identifier DRKS00014996 ( http://www.drks.de/DRKS00014996 ).

What are the critical steps in processing blood cultures? A prospective audit evaluating current practice of reporting blood cultures in a centralised laboratory serving secondary care hospitals

AIMS

To assess current procedures of processing positive blood cultures against national standards with an aim to evaluate its clinical impact and to determine the utility of currently available rapid identification and susceptibility tests in processing of blood cultures.

METHODS

Blood cultures from three secondary care hospitals, processed at a centralised laboratory, were prospectively audited. Data regarding processing times, communication with prescribers, changes to patient management and mortality within 30 days of a significant blood culture were collected in a preplanned pro forma for a 4-week period.

RESULTS

Of 2206 blood cultures, 211 positive blood cultures flagged positive. Sixty-nine (3.1%) of all cultures were considered to be contaminated. Fifty per cent of blood cultures that flagged positive had a Gram stain reported within 2 hours. Two (0.99%) patients with a significant bacteraemia had escalation of antimicrobial treatment at the point of reporting the Gram stain that was subsequently deemed necessary once sensitivity results were known. Most common intervention was de-escalation of therapy for Gram-positive organisms at the point of availability of pathogen identification (25.6% in Gram positive vs 10% in Gram negative; p=0.012). For Gram-negative organisms, the most common intervention was de-escalation of therapy at the point of availability of sensitivity results (43% in Gram negatives vs 17.9% in Gram positive; p=0.0097). Overall mortality within 30 days of a positive blood culture was 10.9% (23/211). Antibiotic resistance may have contributed to mortality in four of these patients (three Gram negative and one Gram positive).

CONCLUSION

Gram stain result had the least impact on antibiotic treatment interventions (escalation or de-escalation). Tests that improve identification time for Gram-positive pathogens and sensitivity time for Gram-negative pathogens had the greatest impact in making significant changes to antimicrobial treatment.