False-positive Blood Culture Results Research Articles

Double Blood Culture Policy Is More Effective Than Single In Neonatal Intensive Units

Aim: Blood culture (BC) sampling and antibiotic administration are common practices in Neonatal Intensive Care Units(NICUs). However, false positive BC results might affect clinician’s decision and lead to inappropriate antibiotic treatments. The aim of this study was to investigate the effect of double culture on clinical application.
 Material and Methods: The study was conducted retrospectively. The blood culture results of the patients admitted to the NICU between 2016-2019 were analyzed. Considering sepsis before 2017, we took only one sample from the patient. After this period, we started to take double blood cultures. Time frames of BCs were investigated to two groups as early and late onset sepsis fistly, and then subgroups as; a-) Group 1, BCs in the first 24 hours, b-)Group 2, between 24 to 72 hours, and c-)Group 3, after 72 hours. 
 Results: Total of 1747 BC samples were taken in study. Majority of BCs were in Group 3(62%). Male/female ratio was 1.3:1. Staphylococcus Epidermidis(S. Epi) was major source for the contamination. But, by taking dBCs, we were able to eliminate most S.Epi contamination in Group 2 (11%vs.3%) and in Group 3(41%to14%). We were able to identify some resistant Gr(-) pathogens in one arm although the other arm was negative, by taking dBC.
 Conclusions: Our study indicates that dBC policy in NICUs could help to clinicians for judicious decision in antibiotic use and decrease unnecessary antibiotic exposure of infants. Also it could be enable to detect some highly pathogen microorganism easily.
 Key words: Newborn, Septicemia, Blood culture, Coagulase Negative Staphylococci, contamination

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.

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.

False-positive blood culture results in patients with hematologic malignancies

Blood cultures are the most valuable tool when bacteremia is clinically suspected. Technical advances have led to the development of automated blood culture systems to detect bacterial infections. Usually positive signals in automated blood culture systems result from the proliferation of microorganisms. Cases are classified as false-positive when the automated blood culture system produces a positive signal but no microorganisms are detected on Gram-stained smears and no microorganism growth is observed in blood subcultures. False-positive blood culture results are very rare in patients with hematologic malignancies. Recently, we encountered four patients who had false-positive blood culture results. Two of the patients were diagnosed with acute leukemia, involving hyperleukocytosis and an excess of blasts. The other two patients were diagnosed with acute leukemia and diffuse large B cell lymphoma with leukocytopenia. Although hypercapnia or acidosis, apart from hyperleukocytosis, might also cause false-positive results, our cases clearly did not have these conditions. We should be aware of the possibility that false-positive blood culture results can occur in patients with leukocytopenia, as well as hyperleukocytosis. To understand the mechanisms responsible for the observed false-positive results, additional studies are needed after the accumulation of similar cases.

PS-214 Does A Total Sterile Collection Bundle Reduce False Positive Blood Culture Rates And Antibiotic Use In Neonatal Intensive Care?

Background and aim In neonatal intensive care coagulase negative Staphylococcus species can be both blood culture contaminant and pathogen. False positive cultures can result in clinical uncertainty and unnecessary antibiotic use. Our aim was to assess the effect of a total sterile blood culture collection bundle on the incidence of false positive blood cultures in a regional surgical neonatal intensive care unit. Method Clinical data of all infants who had blood cultures taken before and after the introduction of the collection bundle (sterile technique and 2% Chlorhexidine) were collected. The rates of false positive blood cultures, defined as the presence of a skin commensal and <3 predefined clinical signs (Modi et al . 2009), were compared. Results In total 367 blood cultures from 294 babies were assessed, 197 pre-intervention (PRE) and 170 following bundle introduction (POST). The median birth weight and gestation were similar in both groups. The rate of false positive cultures in the total PRE group was 9/197 (4.6%) compared to 1/170 (0.6%) in the POST group (p < 0.05). In infants <28 weeks’ the rates reduced from 4/29 (13.8%) to 0/30 (0%) (p < 0.05). Unnecessary antibiotic exposure rate was 7.7% in the PRE group versus 0.0% in the POST group (p < 0.05). Conclusion Implementation of this collection bundle reduced the number of false positive blood culture results. This has a potential benefit in reducing unnecessary antibiotic use and associated health care costs.

Investigating the Impact of Blood Culture Bundles on the Incidence of Blood Culture Contamination Rates

Blood cultures are integral diagnostic procedures for identifying serious infections and selecting antimicrobials. Positive blood cultures are the initial step in attaining a conclusive diagnosis of sepsis. Relative risk is blood culture contamination, false-positive blood culture results, diagnostic error delays, treatment errors, excessive lab testing, and increased length of stay. A complicating issue is the increased use of central venous access devices (CVADs). The purpose of this descriptive, comparative study is to evaluate the effectiveness of blood culture bundles on blood cultures drawn through a CVAD and contamination rates. The study revealed a decrease in blood culture contamination rates by 61%.

Blood cultures: towards zero false positives

The culture of micro-organisms from blood is an essential laboratory test for the diagnosis of bacteraemia. Early positive results provide valuable diagnostic information on which appropriate antimicrobial therapy can be initiated. Like any tests, however, false-positive blood culture results can limit the utility of this important tool. These false-positive results arise due to contamination. Reports from NHS trusts and equipment suppliers suggest these contamination rates could be as high as 10% (Department of Health (DH), 2007). A variety of strategies have been investigated and employed to decrease contamination rates. This article describes the utility of a variety of approaches to reduce the number of false-positive percutaneous blood cultures specifically in the adult population.

Review of Clinical Trials of Skin Antiseptic Agents Used to Reduce Blood Culture Contamination

False-positive blood culture results may lead to prolonged hospitalization, inappropriate antibiotic administration, and increased healthcare costs. We conducted a review of the literature to assess the effect of skin antiseptic agents on the rate of false-positive blood culture results. We found no clear evidence to suggest which antiseptic should be used to prevent false-positive results. Studies suggest, however, a possible benefit from the use of prepackaged skin antiseptic kits and alcohol-containing antiseptics.

Preventing Contaminated Blood Cultures -- Don't Use Intravenous Catheters!

Experienced clinicians are well aware of the costs in time and money of false-positive blood culture results. To minimize venipunctures, staff members at pediatric and emergency departments frequently obtain blood for cultures when they insert intravenous catheters. Unfortunately, although this approach may decrease patient discomfort, it may be associated with …

Blood Cultures in the Critical Care Unit: Improving Utilization and Yield

Sepsis is a common cause of morbidity and death in critically ill patients, and blood culture samples are often drawn in an effort to identify a responsible pathogen. Blood culture results are usually negative, however, and even when positive are sometimes difficult to interpret. Distinguishing between true bacteremia and a false-positive blood culture result is important, but complicated by a variety of factors in the ICU. False-positive culture results are costly because they often prompt more diagnostic testing and more antibiotic prescriptions, and increase hospital length of stay. A number of factors influence the yield of blood cultures in critically ill patients, including the use of antibiotics, the volume of blood drawn, the frequency with which culture samples are drawn, and the site from which the culture samples are taken. Skin preparation techniques, handling of the cultures in the microbiology laboratory, and the type of blood culture system employed also influence blood culture yield. Attempts to identify predictors of true bacteremia in critically ill patients have been disappointing. In this review, we discuss factors that influence blood culture yield in critically ill patients, suggest ways to improve yield, and discuss true bacteremia vs false-positive blood culture results. We also discuss the costs and consequences of false-positive blood culture results, and list noninfectious causes of fever in the ICU.

Financial and Clinical Impact of False‐Positive Blood Culture Results

During a 4-year period, 9465 specimens for blood culture were obtained from 11,911 highly febrile, otherwise healthy young children. Of these specimens, 87 (0.9%) yielded nonpathogens and were considered to be false-positive blood culture results (FPBCRs). Seventy-two of the patients who provided these specimens were treated on an outpatient basis (resulting in $10,821 in treatment charges), and 7 were admitted to the hospital (resulting in $16,200 in charges) as a result of the FPBCRs. Studies performed during follow-up included a second blood culture (21 patients), complete blood cell count (11), urine analysis and culture (5), lumbar puncture (3), and chest radiography (3). Only a small minority of patients were hospitalized or underwent invasive procedures. The charges associated with FPBCRs are very small in comparison to the initial charges of culturing specimens obtained from children considered to be at risk. Concern about the consequences of FPBCRs should not deter clinicians from performing indicated cultures for children who potentially have bacteremia.

Mima polymorpha Bacteremia

Over a ten-month period 56 blood cultures from 27 patients grew Mima polymorpha. Only three patients in this group had clinical evidence of bacteremia. Most of the 48 positive blood cultures in the 24 patients without clinical evidence of bacteremia were caused by addition to the blood cultures of penicillinase, which was contaminated with M polymorpha. Several patients were treated because of the false-positive blood culture results.

Mima polymorpha bacteremia. False-positive cultures due to contaminated penicillinase

Over a ten-month period 56 blood cultures from 27 patients grew Mima polymorpha. Only three patients in this group had clinical evidence of bacteremia. Most of the 48 positive blood cultures in the 24 patients without clinical evidence of bacteremia were caused by addition to the blood cultures of penicillinase, which was contaminated with M polymorpha. Several patients were treated because of the false-positive blood culture results.