False-positive Blood Cultures Research Articles

Impact of quality improving interventions on blood culture contamination rate- A prospective observational study

Background: Blood cultures (BC) is the gold standard for diagnosis of bacteremia but false positive blood cultures due to specimen contamination can lead to increased usage of unnecessary antibiotics and have negative impact on antimicrobial stewardship program. Overgrowth of contaminants can also obscure growth of genuine pathogens and hamper accurate diagnosis. The aim of this study is to evaluate effectiveness of Quality improving (QI) interventions to reduce the blood culture contamination rate Material and Methods: Prospective observational study, conducted at a public sector hospital, for a total duration of 6 months. A taskforce developed and implemented QI interventions to reduce blood culture contamination, and evaluated effectiveness of these interventions by comparing contamination rates prior to and after implementation of the intervention. Results: The post-intervention average contamination rate was significantly lower with the mean contamination rate of 4.7 ± 1.5% as compared to baseline BC contamination rate which was 10.6 ± 1.8% (p=0.013) Conclusion: Quality improving (QI) interventions significantly reduced the blood culture contamination rate. Keywords: Quality improvement, Interventions, Blood culture, Contamination.

The impact of the COVID-19 pandemic on blood culture practices and bloodstream infections.

Bacterial infections are a significant cause of morbidity and mortality worldwide. In the wake of the COVID-19 pandemic, previous studies have demonstrated pandemic-related shifts in the epidemiology of bacterial bloodstream infections (BSIs) in the general population and in specific hospital systems. Our study uses a large, comprehensive data set stratified by setting [community, long-term care (LTC), and hospital] to uniquely demonstrate how the effect of the COVID-19 pandemic on BSIs and testing practices varies by healthcare setting. We showed that, while the number of false-positive blood culture results generally increased during the pandemic, this effect did not apply to hospitalized patients. We also found that many infections were likely under-recognized in patients in the community and in LTC, demonstrating the importance of maintaining healthcare for these groups during crises. Last, we found a decrease in infections caused by certain pathogens in the community, suggesting some secondary benefits of pandemic-related public health measures.

Evaluating the Proportion of Low-Value Blood Cultures Obtained in a Pediatric Emergency Department.

Existing literature suggests that for some pediatric conditions, blood cultures may be of low value in specific clinical circumstances. The goals of our study were to: 1) identify common pediatric illnesses and define criteria for low-value blood cultures in children aged from 91 days to 19 years, 2) apply these criteria retrospectively to identify the patients in our emergency department (ED) who had low-value blood cultures obtained, and 3) describe this cohort and assess the proportion of true bacteremia in low-value blood cultures. The study team reviewed the literature and developed consensus criteria to identify conditions in which blood cultures were of low value for our study population. The criteria were applied retrospectively to well-appearing patients aged from 91 days to 19 years, without a central venous catheter, and evaluated in our ED with a peripheral blood culture from June 2018 to April 2020. Children admitted to the intensive care/hematology-oncology/cardiology/pulmonary units, those transferred from our ED to an outside facility, who transferred to our ED due to a positive blood culture from an outside facility, and repeat visits of a patient within 30 days from a previous visit were excluded from the study. After chart review, children with fever for 7 days or more, who were unvaccinated, immunosuppressed, had implanted devices, had a complex medical history, or had provider concerns for bacteremia/sepsis were excluded. The study population consisted of 1436 children. Children at risk for bacteremia (n = 718) were excluded. Four hundred twenty-four children had discharge diagnoses not included in our study. There were 294 (20.5%) patients who had low-value cultures per our study criteria. Nine children (9/294, 3.1%) had false-positive blood cultures, and three (3/294, 1.0%) had true-positive blood cultures. We identified a cohort of patients in our ED with blood cultures obtained when available literature indicates they were of low value.

Evaluation of blood culture samples for contamination and assessment of possible causes

Blood is an enriched growth medium for the growth of microorganisms. Blood culture is the key test for diagnosis of bacteremia and fungemia in patients. A false positive blood culture (blood culture contaminants) is a challenge for both consultants and microbiologists as well. This study based on highlighting source of blood culture contamination and ways of prevention in laboratory and hospitals.

Monocyte distribution width (MDW) as a useful indicator for early screening of sepsis and discriminating false positive blood cultures.

Severe sepsis and septic shock are the leading cause of in-hospital death. As sepsis progresses, expression and activity of endogenous mediators of inflammation change. Early detection of biomarkers can play a role in sepsis screening and in improvement of patient outcomes. Recent studies suggest that increase in monocyte volume may be helpful in early detection of sepsis. Therefore, we evaluated the utility of monocyte distribution width (MDW) for the early assessment of sepsis compared with the blood culture and other inflammatory biomarkers. Medical records of 1,404 patients (aged ≥19 years) who were admitted to the emergency department owing to clinically suspected infectious disease and requested blood cultures from Oct 2019 to Jan 2021 were reviewed. The patients were grouped based on Sepsis-3 criteria. They had undergone other laboratory tests to evaluate their clinical status. MDW was analyzed using DxH900 hematology analyzer (Beckman Coulter, Brea, California, USA). To determine the diagnostic performance of MDW, C-reactive protein (CRP), and procalcitonin (PCT) for sepsis, the area under the curve (AUC) of receiver operating characteristics curves and their sensitivity and specificity were measured. Among 1,404 patients, 520 patients were designated the sepsis group based on Sepsis-3 criteria. In the sepsis group, MDW value was 24.1 (median, IQR 21.6-28.1); AUC values for MDW, CRP, and PCT were 0.67 (95% CI, 0.64-0.69), 0.66 (95% CI, 0.63-0.68), and 0.75 (95% CI, 0.72-0.77), respectively. For diagnosis of the sepsis, the cut-off value of MDW was 21.7 (sensitivity 74% and specificity 54%). Measured values of MDW were higher for the blood culture positive group than that of the blood culture contamination group (P<0.001, 95% CI, -5.9 to -3.0) or blood culture negative group (P<0.001, 95% CI = -5.8 to -4.2). MDW is a new hematological parameter that is simultaneously calculated during complete blood cell counting by Beckman Coulter hematology analyzer. MDW is expected to serve as a useful indicator for early screening of sepsis in conjunction with CRP and PCT. MDW is especially useful for sepsis assessment in patients with a suspected infection. MDW can also assist in discriminating false positive blood cultures.

The absolute number of leukocytes per vial as a major cause of early false positive blood cultures: proof-of-concept and application.

Blood cultures detected as positive by the automated system but negative by microscopy and subculture are considered as "false-positives." Several causes have been identified, including hyperleukocytosis or the presence of fastidious bacteria, but as many cases remain unexplained we aimed to investigate the false positives occurring in our laboratory. We retrospectively collected data on blood cultures received over a period of 12months to determine factors associated with the false-positive vials. We then prospectively validated our findings on the false-positive results occurring over a 3.5-month period. We finally applied scanning electron microscopy (SEM) on 63 false positives and molecular approaches on a subset of them. In the retrospective study, 154 (85%) of the 181 false-positive identified were positive following less than 4h of incubation and were considered as "early false-positives." By performing ROC curves on these early false positives, we demonstrate that the absolute number of leukocytes is in fact the most discriminating factor of early false positivity (p < 0.001). This phenomenon can be the consequence of either a high blood culture volume (p < 0.001) or hyperleukocytosis (p < 0.001). In the prospective study, the use of a threshold of 219 million of leukocytes per vial enabled the identification of 97% of the early false positives. Finally, SEM and specific qPCR enabled three additional identifications while 16S rRNA/nanopore sequencing enabled the detection of Helicobacter cinaedi bacteremia and a polymicrobial infection. A high absolute number of leukocytes in blood cultures explains most false positives, thereby making it possible to target additional microbiological investigations.

Evaluation of advanced practice provider related return visits to a pediatric emergency department and their outcomes.

While multiple studies have evaluated physician-related return visits (RVs) to a pediatric emergency department (PED) limited data exists for Advanced Practice Provider (APP)-related RVs, hence our study aimed to evaluate APP-related RVs and their outcomes in a PED. We conducted a retrospective review of 72-h RVs where clinical care was independently provided by an APP during the index visit from January 2018 to December 2019. We extracted patient demographics, index and return visits' characteristics and outcomes. Reasons for RVs were categorized as progression of illness, medication-related, callbacks and others. Index visits were assessed for any diagnostic errors; impact of which to the patient was classified as none, minor or major. Our APP-related RV rate was 2.1% (653/30,328). 462 eligible RVs were included in the final analysis. Majority of RVs were for medical reasons (n=442, 95.7%); lower acuity (Emergency Severity Index ≥3, n=426, 92.2%); due to persistence/progression of illness (n=403; 87.2%) with viral illness being the common diagnosis (n=159; 34.4%). 12 (2.6%) RVs were secondary to callbacks (8 radiology callbacks; 4 false positive blood cultures). Diagnostic errors were noted in 14 (3%) encounters of which 3 resulted in a major impact; radiological (7 fractures) and ophthalmological (2 corneal abrasions and 2 foreign bodies) misses constituted the majority of these. APP-related RVs for low acuity medical patients remain low and are associated with good outcomes. Diagnostic errors account for a minority of these RVs. Focused interventions targeting provider errors can further decrease these RVs.

Assessment of Factors Influencing the Positivity of Blood Culture by BacT/ALERT®3D Microbial Detection System: A Cross-sectional Observational Study

Introduction: Bloodstream Infections (BSI) are defined as the presence of living microorganisms in the blood. It is a systemic condition that can result in life-threatening sepsis, thus leading to high morbidity and mortality. Blood cultures have become critically important. Positive blood culture results can help a clinician’s early diagnosis and start empirical antimicrobial at the correct time. Today many laboratories use modern, automated, continuous-monitoring blood culture systems for the detection of bacterial growth for blood culture. At our hospital, blood culture is done by using automated detection in BacT/Alert instrument (Biomerieux, France). Aim: To determine the effect of a number of blood cultures and volume of blood on positivity rates, contamination rate in blood cultures, and rate of false-positive blood cultures. Materials and Methods: Present study was a cross-sectional observational study conducted from 1st May 2019 to 31st July 2019. Blood culture requests of all patients were included in the study. All blood culture bottles were processed as per standard laboratory protocols. The effect of a number of blood cultures and amount of blood volume on positivity rate, contamination rate, and false-positive blood cultures were studied in detail. The patient’s details and microbiological result parameters were extracted from Laboratory Information System (LIS). All the data was analysed in Microsoft Excel 2010. Results: A total of 761 blood culture bottles were received at the Microbiology laboratory from 604 patients. Maximum (30%) blood cultures were received from 0-10 years of age group. A total of 31% (236/761) of blood cultures were positive. The true pathogen positivity rate was 41.1% and the contamination rate was 58.9%. Single (74.4%) blood culture requests were more than two (25.3%) or three (0.3%) blood cultures. True pathogens were isolated in 9% (41/449) of single blood cultures and in 18% (56/306) of two blood cultures. Overall, 42% of blood cultures had adequate volume and 58% of blood cultures had inadequate volume. However, the true pathogen positivity rate was 14% (61/444) from bottles with inadequate volume and 11% (36/317) from bottles with adequate volume. Out of 236 positive blood cultures, 139 (59%) were identified as contaminants. A total of 5/761 (0.7%) blood cultures were identified as false positive blood cultures. Conclusion: Based on the study findings, a step should be taken to discourage single blood culture and to encourage multiple blood cultures for the diagnosis and better patient care. Although, volume of blood is important, inadequate volume did not affect true pathogen positivity rate in present study. Contamination rate of blood cultures is a major concern and regular training of the concerned staff regarding strict asepsis should be implemented.

Patient-specific risk factors contributing to blood culture contamination.

Contaminated blood cultures result in extended hospital stays and unnecessary antibiotic therapy. Patient-specific factors associated with blood culture contamination remain largely unexplored. Identifying patients at higher risk of blood culture contamination could alert healthcare providers to take extra precautionary measures to limit contamination in these patients, and thereby prevent associated adverse outcomes. We sought to identify patient-related factors that contribute to blood culture contamination in hospitalized patients. We conducted a secondary data analysis of a retrospective cohort study at an academic medical center. Study participants included 19,255 adult patients who had blood culture(s) performed during a hospital admission between June 2014 and December 2016. Data were analyzed to evaluate risk factors for blood culture contamination using logistic regression. Among adult patients, we identified 464 contaminated episodes and 11,010 negative blood-culture episodes. Chronic obstructive pulmonary disease (adjusted odds ratio [AOR], 1.67; 95% confidence interval [CI], 1.20-2.34) and stay in an intensive care unit (ICU) during an admission (AOR, 1.41; 95% CI, 1.14-1.74) were associated with blood culture contamination. Other risk factors included race, body mass index, and admission from the emergency department. Subgroup analyses of patients admitted from the emergency department showed similar results. We identified patient-specific factors that increase the odds of false-positive blood cultures. By introducing mitigation strategies to limit contamination in patients with these risk factors, it may be possible to reduce the adverse clinical impact of blood culture contamination.

1360. Prevalence of Bacteremia in Hospitalized Patients with Skin and Soft Tissue Infections (SSTI)

BackgroundSkin and soft tissue infections (SSTI) are common in outpatient and inpatient settings. The prevalence of positive blood cultures (BC) ranges from 2% to 52%. Because of the variations in published data, the exact prevalence of bacteremia in hospitalized patients with SSTI is unknown. Our objective is to determine the prevalence of bacteremia in hospitalized patients with SSTI.MethodsRetrospective chart review from January 2017 to December 2018. Patients older than 18 years admitted with SSTI who required BC on admission were included. Patients who met the criteria for systemic inflammatory response syndrome (SIRS)/sepsis or severe SSTI, or had an underlying immunodeficiency underwent BC collection. Patients with diabetic foot ulcer, device related SSTI, necrotizing fasciitis, and osteomyelitis were excluded. Patients were divided into 3 groups: true positive (TP) defined as a true pathogen, false positive (FP) defined as a contaminant, and true negative (TN) defined as no growth in BC. Physician assessment, microorganisms isolated, number of positive bottles/culture sets, and timing of growth were reviewed. Patients’ comorbidities, presence of SIRS, laboratory data, duration of antibiotic use, and length of stay (LOS) were compared.ResultsWe screened 583 patients and included 541 patients. The mean age was 62 ± 18.4 years, and 60% were male. 47/ 541 (8.6%) had skin abscesses. 57 patients (11%) had positive BC, of whom 32 were TP (6%), and 25 were FP (5%). 89% of patients (484) had TN BC. The organisms isolated are described in Figures 1 and 2. Patients in the FP and TN groups had prior antibiotic use, compared to TP (P< 0.05). The FP group had a longer LOS and duration of antibiotic use compared to the TN group (p< 0.05). 76% of FP had repeated BC. Beta-lactam antibiotics were mostly used, followed by anti-MRSA antibiotics (40%). We did not find risk factors to predict the likelihood of bacteremia. The outcome was not different among the 3 groups.Figure 1. Microorganisms isolated from blood cultures of patients with SSTI – True pathogens Figure 2. Microorganisms isolated from blood cultures of patients with SSTI – Isolated contaminants ConclusionThere was a low incidence of true bacteremia (6%) in hospitalized patients with SSTI. More than 90% of TP were predictable causal microorganisms, which are covered by empiric antibiotics. BC may not affect the initial treatment of SSTI. FP BC were associated with an increased LOS, longer antibiotic use, and increased healthcare cost.Disclosures All Authors: No reported disclosures

Blood Culture Contamination in a Community Hospital- less than 2% is achievable

Abstract Introduction/Objective Blood cultures are commonly obtained to evaluate the presence of bacteria or fungal infection in a patient’s bloodstream. The presence of living microorganisms circulating in the bloodstream is of substantial prognostic and diagnostic importance. A positive blood culture indicates a reason for the patient’s illness and provides the etiological agent for antimicrobial therapy. Collection of blood culture is an exact process that requires time, the proper order of draw, and following of correct protocol. The busy Emergency department that requires multiple demands for nurse’s time, turnover of staff, rushing from one task to another can result in the improper collection and false-positive blood cultures. The national benchmark is set at 3% by the American Society of Clinical Microbiology (ASM) and The Clinical and Laboratory Standard Institute (CLSI). False-positive blood culture results in increased length of stay and unnecessary antimicrobial therapy, resulting in an increased cost burden to the hospital of about $5000 per patient. Methods/Case Report At our 150-bed community hospital, 26 beds Emergency Department, we have come a long way in reduction of our blood culture contamination rates from upwards of 4% to less than 2%, far lower than the national benchmark. Results (if a Case Study enter NA) NA Conclusion There are multiple devices available from various manufacturers claiming to reduce blood culture contamination. These devices do reduce blood culture (BC) contamination but at an added cost of the device. The rate of BC can be reduced and less than 3% is achievable by materials available in the laboratory. We have achieved this by providing training to every new staff by demonstration and direct observation, providing everything required for collection in a kit, using proper technique, the inclusion of diversion method that involves the aseptic collection of a clear tube before collecting blood cultures, and following up monthly on any false positive blood cultures.

Reduction of False-positive Blood Culture Rates Using a Passive Blood Diversion Device in an Urban Academic Pediatric Emergency Department

Background Blood cultures contaminated with common commensals during collection contribute to antibiotics overuse, return visits to the Emergency Department (ED), and increased overall medical costs. There are published quality improvement projects aimed at implementing best practices to reduce false positive blood culture (FPBC) rates in adults, but literature is lacking in pediatrics, and few studies include the use of passive diversion devices designed to remove an aliquot of blood likely to contain skin flora. FPBC rates in our pediatric ED range from 0.45% to 5.63%. Our FPBC institutional goal is Methods In an urban, academic, freestanding pediatric hospital, the ED has 35,000 patient encounters and obtains 2800 blood cultures annually. In each study period, passive blood diversion devices were bundled with collection supplies. Education with best practices for technique, use of the device, and instructions to record device non-use were provided. Positive blood culture results were reviewed by the Infection Preventionist to determine true infection versus FPBC. Results In the first study period, 341 blood cultures were drawnwith an overall FPBC rate of 1.5%. The rate of FPBC when the device not used was 10.5% (4 of 38). In the second study period, 905 blood cultures were drawn with an overall FPBC rate of 0.22%. The rate of FPBC when the device not used was 6.06% (2 of 33). Zero FPBCs occurred with device use in each study period (0 of 303) and (0 of 874). Conclusions This significant reduction (by Fisher's exact test p = 0.0001) suggests that employing a passive blood diversion device in addition to targeted education may decrease FPBCs; antibiotics overuse, costs, and return visits in the pediatric ED setting.

Emergency Department Observes 83% Reduction in Blood Culture Contamination with Initial Specimen Diversion Technology Adoption

Background Blood culture attempts to reduce unfavorable outcomes for patients with bloodstream infections by guiding antibiotic therapy. False positive blood culture results are frequent (a 3% contamination rate is considered standard) and associated with unnecessary broad-spectrum antibiotic usage, extended hospital stays and elevated clinical costs. Diversion of the initial portion of a blood sample (which can host deep skin flora associated with venipuncture-dislodged skin fragments) is proposed to address an avenue for contamination unaddressed by conventional blood culture protocol. Methods Blood culture sets were obtained from adult patients during an 18-month observation period in a 32-bed emergency department in California for a non-randomized prospective controlled cohort study. Blood cultures were obtained using either conventional methods (venipuncture and intravenous catheter start) or with initial specimen diversion technology (in tandem with venipuncture and intravenous catheter start). Blood culture bottle tops were disinfected with alcohol pads and patient skin was prepared with a 30-second chlorhexidine gluconate solution scrub. Samples were considered contaminated if skin flora were present in either the aerobic or anaerobic bottle of a single blood culture set. Results Conventional methods were utilized to collect 3,170 blood cultures, from which 77 (2.43%) were contaminated, while initial specimen diversion technology was utilized to collect 2,168 blood cultures, from which 9 (0.42%) were contaminated. Conclusions Use of initial specimen diversion technology was associated with an 83% lower rate of blood culture contamination compared to conventional methods, sustained for 18 months. Lower rates of blood culture contamination translate to reduced administration of unnecessary antibiotics (diagnostic stewardship and antimicrobial stewardship), reduced patient length of stay, and reduced clinical expenditures.

G-control Charts for Contamination Rates of Blood Cultures in a University Hospital

Objective: To determine blood culture contamination rates, and display with a g-chart.Materials and Methods: The medical records of patients, from whom blood cultures were obtained in a university hospital, during January and December 2019 were retrieved and reviewed for contamination. The Center for Disease Control and Prevention (CDC) criteria were used to classify the blood culture results. The contamination rates were illustrated with a g-chart.Results: We identified 331 false-positive blood cultures, among 32,961 cultured specimens; yielding a contamination rate of 1.0% (95%CI = 0.9% – 1.1%). The highest contamination events occurred in the Emergency department (49.2%), Pediatric ICU (5.2%) and Neonatal ICU (4.8%), respectively. The most common commensal bacterial genus were Staphylococcus coagulase negative (67.1%), Bacillus spp. (10.2%) and Corynebacterium spp. (7.6%), correspondingly. The g-charts could identify 14 abnormal variations, in 41 locations.Conclusion: The contamination rates found were within ranges of other reports. G-charts are simple to construct, easy to interpret and sensitive for detection of real time epidemics.

Role of Hand Hygiene and Sterile Blood Sampling in Reduction of False Positive Blood Cultures from a Neonatal Intensive Care Unit of a Rural Teaching Hospital: A Quasi-experimental Study

Introduction: Blood culture remains the gold standard for diagnosis of newborn infections. Its contamination not only results in inadvertent use of antimicrobials against the false positives but also causes substantial financial burden and patient safety concerns. There are various ways to reduce blood contamination, of which hand hygiene and sterile blood sampling are most crucial. Aim: To evaluate and reduce the blood contamination rate and false positive blood cultures from the Neonatal Intensive Care Unit (NICU). Materials and Methods: The prevalent bacteriology and Blood Culture Contamination Rate (BCCR) at the NICU was assessed by a retrospective study on all the neonates with suspected sepsis who had blood culture at admission. Healthcare workers at NICU were observed for their hand wash and sterile blood sampling technique by dedicated team members. Identified deficiencies among them were intervened by an educational model with regular training and reinforcement on hygienic practices for three months. Postintervention prospective study was done on all the neonates with suspected sepsis who had blood culture at admission. During this period the same educational model continued, to know its efficacy in reduction of blood contamination and change of bacteriology pattern. Data collected was entered into Microsoft excel sheet 2010 version and analysed using software Stata 14.0 version. Results: Preintervention blood culture reports of 205 neonates screened for sepsis showed 58 (28.3%) samples with positive growth. Of this, 18 were contaminants, 31 were Coagulase Negative Staphylococci (CoNS), three gram negative and six gram positive organisms with blood contamination rate of 8.7%. Blood culture reports of postintervention study on 200 neonates screened for sepsis showed 41 (20.5%) samples positive for growth. Bacteriology showed 12 contaminants, 13 CoNS, eight gram positives, seven gram negatives and one fungal growth with BCCR of 6%. After intervention growth of CoNS was reduced which was statistically significant (p&lt;0.05). Conclusion: Simple inexpensive education programme helps the healthcare workers to follow the standard technique of hand wash and sterile blood sampling which goes a long way in reducing blood culture contamination.

Screening for Bacteremia in Trauma Patients: Traditional Markers Fall Short.

Deranged physiology in trauma complicates the clinical identification of sepsis, resulting in overscreening for bacteremia. No clinical signs or biomarkers accurately diagnose sepsis in this population. Our objective was to evaluate the accuracy of the current criteria used to prompt screening for bacteremia in trauma patients and determine independent predictors of bacteremia. Adult trauma patients admitted to our level I academic trauma center who had blood cultures (BCs) drawn were identified. Those with positive BCs were compared to those with negative or false positive BCs. False positive was defined as a BC deemed contaminated and not treated at the discretion of the attending physician. Over a 2-year period, 366 trauma patients had BCs drawn. After excluding surveillance cultures (those drawn to demonstrate bacteremia clearance), 492 unique BC sets were evaluated; 104 (21.1%) BC sets were positive; 30 (28.8%) of these were falsely positive, resulting in a true-positive rate of 15% in the screened population. Univariate analysis suggested temperature and heart rate were associated with positive BC, while multivariable analysis found only the presence of a central line and lactic acid to be predictive. Procalcitonin (PCT) was poorly predictive, with a positive predictive value of 18% and a negative predictive value of 91%. Current tools for identifying bacteremia in trauma patients result in overscreening. PCT may have a limited role as a negative predictor for bacteremia. Given that false-positive BCs have negative patient and economic consequences, future study should focus on development of alternative screening modalities.

Passive Engineering Controls Result in Sustained 66% Reduction in Blood Culture Contamination

Background: Blood culture testing is an important diagnostic tool in identifying the presence of microbes in the bloodstream. Tests are frequently contaminated, leading to false-positive results. Blood culture contamination can result in unnecessary antibiotic treatment, extended hospital length of stay, and patient exposure to hospital-acquired conditions. Methods: St. Mary’s Regional Medical Center (SMRMC) in Russellville, Arkansas, struggled with blood-culture contamination rates, with an average of 6.8% from 2014 to 2018. Ongoing staff education yielded a reduction to an average of 5%. In an effort to reduce the contamination rates, our facility elected to try a novel specimen diversion device. Laboratory and emergency department (ED) staff were educated on the diversion device prior to the initiation of the trial period. Compliance with the diversion device averaged 70%–75% during the trial period. Monitoring of contaminations was added to our daily safety huddle to provide a quick turnaround time for false-positive education to specific clinical staff. Results: The results were significant, with a decrease in contamination rates from 4.93% to 1.66%—a 66% reduction. Improved blood culture testing has several advantages: best practice for patient care is first and foremost, along with other financial benefits for the facility. Several articles have estimated the cost of a contaminated culture to be $3,000–$10,000 per event; SMRMC has adopting an estimated cost of $4,000. The number of cultures at our hospital averages ~4,400 per year, and these results suggest a savings of &gt;$500,000 per year (as contaminations on an annual basis fell from 217 to 73). With this intervention, 144 patients were spared from receiving unnecessary antibiotics as a result of a false-positive blood culture testing. Conclusions: We conducted a brief analysis to determine whether there was any obvious change in length of stay for patients with a false-positive blood culture compared to those with true negative results. In analyzing data for 3 different months, patients with contaminated cultures spent an average of 3.97 additional days in the facility. In conclusion, the implementation of this specimen diversion device significantly lowered our contamination rates, was integrated into practice, and has provided clinical and financial benefits.Funding: NoneDisclosures: None

False-Positive Blood Cultures: The Need for Follow-up

AbstractThe diagnosis of blood-borne infections in immunocompromised patients is a major challenge for the clinical microbiology laboratory. Isolation of bloodborne pathogens in these patients has profound clinical implications, yet is fraught with technical problems, including the presence of unusual and difficult to isolate pathogens. Coupled with this is the problem of false-positive blood culture signals from automated blood culture systems which further delays the definitive diagnosis. Here, we present a case of an 8-year-old boy with Ph +ve acute lymphoblastic leukaemia who has repeated ‘false positive’ blood cultures and later grew an uncommon organism.

Using Machine Learning to Predict Bacteremia in Febrile Children Presented to the Emergency Department.

Blood culture is frequently used to detect bacteremia in febrile children. However, a high rate of negative or false-positive blood culture results is common at the pediatric emergency department (PED). The aim of this study was to use machine learning to build a model that could predict bacteremia in febrile children. We conducted a retrospective case-control study of febrile children who presented to the PED from 2008 to 2015. We adopted machine learning methods and cost-sensitive learning to establish a predictive model of bacteremia. We enrolled 16,967 febrile children with blood culture tests during the eight-year study period. Only 146 febrile children had true bacteremia, and more than 99% of febrile children had a contaminant or negative blood culture result. The maximum area under the curve of logistic regression and support vector machines to predict bacteremia were 0.768 and 0.832, respectively. Using the predictive model, we can categorize febrile children by risk value into five classes. Class 5 had the highest probability of having bacteremia, while class 1 had no risk. Obtaining blood cultures in febrile children at the PED rarely identifies a causative pathogen. Prediction models can help physicians determine whether patients have bacteremia and may reduce unnecessary expenses.

2014. Assessment of Cost, Morbidity, and Mortality Associated with Blood Culture Contamination

BackgroundBlood cultures are the primary diagnostic tool for bloodstream infections, but accuracy of results is dependent on collection technique. Decreasing blood culture contaminations is a priority for antimicrobial stewardship programs as false positives can expose patients to adverse effects of unnecessary antibiotics. In this study, we present an analysis comparing clinical outcomes and cost associated with false-positive and true negative blood cultures at our institution.MethodsWe conducted a single-center, retrospective, case–control study in patients admitted following blood culture collection in the emergency department from 2014 to 2018. Demographic and clinical characteristics were evaluated in patients with false-positive blood cultures (cases) and negative blood cultures (controls). Contaminants were identified per American Society of Microbiology recommendations. Clinical outcomes were compared between cases and controls, and adjusted analyses were performed with logistic regression, linear regression, and generalized linear models controlling for age, race, body mass index, and sepsis. Statistical analysis was performed using SAS 9.4.ResultsA total of 1,102 cases and 11,266 controls were included in analysis. All clinical outcome measures were significantly higher in patients with contaminated blood cultures (see table). Select clinical outcomes remained significant when controlling for potential confounders.ConclusionTo the best of our knowledge, this is the largest study evaluating the clinical and financial impact of blood culture contamination with inclusion of >1,000 cases during a 5-year period. Our study shows that blood culture contamination is associated with increased length of stay, unnecessary exposure to antibiotics and procedures, development of antibiotic-associated adverse events, and higher hospital charges as reported in smaller studies. However, this study is the first to the best of our knowledge reporting increased mortality associated with blood culture contamination. Implementation of innovative strategies to reduce contamination should be pursued. Antimicrobial stewardship programs should prioritize identification of contaminants and rapid de-escalation of inappropriate antibiotics in these patients to improve patient care. Disclosures All authors: No reported disclosures.