Peripheral blood culture contamination in adults and venepuncture technique: prospective cohort study

Laboratory approaches to determining blood culture contamination rates: an ASM Laboratory Practices Subcommittee report

Blood culture contamination (BCC) is the presence of specific commensal and environmental organisms cultivated from a single blood culture set out of a blood culture series and that do not represent true bacteremia. BCC can impact quality of care and lead to negative outcomes, unnecessary antibiotic exposure, prolonged hospital stays, and substantial costs. As part of the laboratory's quality management plan, microbiology laboratory personnel are tasked with monitoring BCC rates, preparing BCC rate reports, and providing feedback to the appropriate committees within their healthcare system. The BCC rate is calculated by the laboratory using pre-set criteria. However, pre-set criteria are not universally defined and depend on the individual institution's patient population and practices. This mini-review provides practical recommendations on elaborating BCC rate reports, the parameters to define for the pre-set criteria, how to collect and interpret the data, and additional analysis to include in a BCC report.

Effect of the introduction of a management bundle for blood culture collection

BACKGROUND

Inappropriate blood collection subjected to blood culture (BC) causes BC contamination and may complicate the diagnose is of infectious diseases. Therefore, we developed a bundle based on the guideline recommendations for appropriate blood collection and examined the effects of bundle introduction.

METHODS

We performed a retrospective analysis of BC samples to determine the contamination rates before and after introducing the BC bundle. We also analyzed the correlation between the compliance rate of the bundle and contamination rate, and between each bundle element and contamination.

RESULTS

After the introduction of the bundle, the contamination rate was significantly reduced from 5.4% ± 0.9% to 1.7± 0.7% (P < .01). The compliance rate of the bundle was significantly associated with a lower contamination rate (P < .01). Multivariable logistic regression showed that collection from superficial veins of the cubital fossa (odds ratio [OR], 0.25; 95% confidence interval [CI], 0.13-0.51, P < .01) and disinfection of the skin at the blood collection site with 1% chlorhexidine alcohol swab (OR, 0.41; 95% CI, 0.25-0.68, P < .01) were significantly associated with lower contamination.

CONCLUSIONS

This study suggests that the introduction of the BC bundle significantly reduced the contamination rate, and bundle compliance was associated with a lower contamination rate.

Diagnosing hospital bacteraemia in the framework of predictive, preventive and personalised medicine using electronic health records and machine learning classifiers

Background

The bacteraemia prediction is relevant because sepsis is one of the most important causes of morbidity and mortality. Bacteraemia prognosis primarily depends on a rapid diagnosis. The bacteraemia prediction would shorten up to 6 days the diagnosis, and, in conjunction with individual patient variables, should be considered to start the early administration of personalised antibiotic treatment and medical services, the election of specific diagnostic techniques and the determination of additional treatments, such as surgery, that would prevent subsequent complications. Machine learning techniques could help physicians make these informed decisions by predicting bacteraemia using the data already available in electronic hospital records.

Objective

This study presents the application of machine learning techniques to these records to predict the blood culture's outcome, which would reduce the lag in starting a personalised antibiotic treatment and the medical costs associated with erroneous treatments due to conservative assumptions about blood culture outcomes.

Methods

Six supervised classifiers were created using three machine learning techniques, Support Vector Machine, Random Forest and K-Nearest Neighbours, on the electronic health records of hospital patients. The best approach to handle missing data was chosen and, for each machine learning technique, two classification models were created: the first uses the features known at the time of blood extraction, whereas the second uses four extra features revealed during the blood culture.

Results

The six classifiers were trained and tested using a dataset of 4357 patients with 117 features per patient. The models obtain predictions that, for the best case, are up to a state-of-the-art accuracy of 85.9%, a sensitivity of 87.4% and an AUC of 0.93.

Conclusions

Our results provide cutting-edge metrics of interest in predictive medical models with values that exceed the medical practice threshold and previous results in the literature using classical modelling techniques in specific types of bacteraemia. Additionally, the consistency of results is reasserted because the three classifiers' importance ranking shows similar features that coincide with those that physicians use in their manual heuristics. Therefore, the efficacy of these machine learning techniques confirms their viability to assist in the aims of predictive and personalised medicine once the disease presents bacteraemia-compatible symptoms and to assist in improving the healthcare economy.

Risk factors and clinical outcomes associated with blood culture contamination

OBJECTIVE

To determine patient-specific risk factors and clinical outcomes associated with contaminated blood cultures.

DESIGN

A single-center, retrospective case-control risk factor and clinical outcome analysis performed on inpatients with blood cultures collected in the emergency department, 2014-2018. Patients with contaminated blood cultures (cases) were compared to patients with negative blood cultures (controls).

SETTING

A 509-bed tertiary-care university hospital.

METHODS

Risk factors independently associated with blood-culture contamination were determined using multivariable logistic regression. The impacts of contamination on clinical outcomes were assessed using linear regression, logistic regression, and generalized linear model with γ log link.

RESULTS

Of 13,782 blood cultures, 1,504 (10.9%) true positives were excluded, leaving 1,012 (7.3%) cases and 11,266 (81.7%) controls. The following factors were independently associated with blood-culture contamination: increasing age (adjusted odds ratio [aOR], 1.01; 95% confidence interval [CI], 1.01-1.01), black race (aOR, 1.32; 95% CI, 1.15-1.51), increased body mass index (BMI; aOR, 1.01; 95% CI, 1.00-1.02), chronic obstructive pulmonary disease (aOR, 1.16; 95% CI, 1.02-1.33), paralysis (aOR 1.64; 95% CI, 1.26-2.14) and sepsis plus shock (aOR, 1.26; 95% CI, 1.07-1.49). After controlling for age, race, BMI, and sepsis, blood-culture contamination increased length of stay (LOS; β = 1.24 ± 0.24; P < .0001), length of antibiotic treatment (LOT; β = 1.01 ± 0.20; P < .001), hospital charges (β = 0.22 ± 0.03; P < .0001), acute kidney injury (AKI; aOR, 1.60; 95% CI, 1.40-1.83), echocardiogram orders (aOR, 1.51; 95% CI, 1.30-1.75) and in-hospital mortality (aOR, 1.69; 95% CI, 1.31-2.16).

CONCLUSIONS

These unique risk factors identify high-risk individuals for blood-culture contamination. After controlling for confounders, contamination significantly increased LOS, LOT, hospital charges, AKI, echocardiograms, and in-hospital mortality.

Successful Reduction of Blood Culture Contamination in an Emergency Department by Monitoring and Feedback

Background:

Blood Culture (BC) contamination is a common problem in the Emergency Department (ED) and is associated with prolonged length of patient stay and excess costs.

Objective:

The study aimed to investigate the impact of monthly monitoring and feedback of BC results on contamination rates.

Methods:

Data from a previous study showed that the contamination rate in the ED consistently exceeded the recommended level. This triggered an ad hoc Quality Improvement team to develop and implement a corrective action plan. In 2017, BC contamination rates were reported to the ED on a monthly basis. In response to this, ED staff conducted intensified educational workshops, followed by private counselling and competency assessment of nurses who collected contaminated BCs.

Results:

A total of 12 educational workshops were conducted in February and March, 2017. The intervention resulted in >60% reduction in the contamination rate, from 8.6% baseline level to less than 3%. Of the 2660 BC sets drawn in 2017 from 1318 patients, 128 (4.8%) were contaminated, accounting for 39.5% of the total number of positive cultures. Sixty percent of the contaminated BCs grew Coagulase-negativeStaphylococcusspecies; other contaminants includedCorynebacteriumspp.,Micrococcusspp.,Propionibacteriumspp.,viridansStreptococcus, andNeisseriaspp.

Conclusion:

Continuous monitoring and feedback of contamination rates reduced BC contamination.

Best Practices of Blood Cultures in Low- and Middle-Income Countries

Bloodstream infections (BSI) have a substantial impact on morbidity and mortality worldwide. Despite scarcity of data from many low- and middle-income countries (LMICs), there is increasing awareness of the importance of BSI in these countries. For example, it is estimated that the global mortality of non-typhoidal Salmonella bloodstream infection in children under 5 already exceeds that of malaria. Reliable and accurate diagnosis of these infections is therefore of utmost importance. Blood cultures are the reference method for diagnosis of BSI. LMICs face many challenges when implementing blood cultures, due to financial, logistical, and infrastructure-related constraints. This review aims to provide an overview of the state-of-the-art of sampling and processing of blood cultures, with emphasis on its use in LMICs. Laboratory processing of blood cultures is relatively straightforward and can be done without the need for expensive and complicated equipment. Automates for incubation and growth monitoring have become the standard in high-income countries (HICs), but they are still too expensive and not sufficiently robust for imminent implementation in most LMICs. Therefore, this review focuses on "manual" methods of blood culture, not involving automated equipment. In manual blood cultures, a bottle consisting of a broth medium supporting bacterial growth is incubated in a normal incubator and inspected daily for signs of growth. The collection of blood for blood culture is a crucial step in the process, as the sensitivity of blood cultures depends on the volume sampled; furthermore, contamination of the blood culture (accidental inoculation of environmental and skin bacteria) can be avoided by appropriate antisepsis. In this review, we give recommendations regarding appropriate blood culture sampling and processing in LMICs. We present feasible methods to detect and speed up growth and discuss some challenges in implementing blood cultures in LMICs, such as the biosafety aspects, supply chain and waste management.

Phlebotomy, a bridge between laboratory and patient

The evidence-based paradigm has changed and evolved medical practice. Phlebotomy, which dates back to the age of ancient Greece, has gained experience through the evolution of medicine becoming a fundamental diagnostic tool. Nowadays it connects the patient with the clinical laboratory dimension building up a bridge. However, more often there is a gap between laboratory and phlebotomist that causes misunderstandings and burdens on patient safety. Therefore, the scope of this review is delivering a view of modern phlebotomy to "bridge" patient and laboratory. In this regard the paper describes devices, tools and procedures in the light of the most recent scientific findings, also discussing their impact on both quality of blood testing and patient safety. It also addresses the issues concerning medical aspect of venipuncture, like the practical approach to the superficial veins anatomy, as well as the management of the patient's compliance with the blood draw. Thereby, the clinical, technical and practical issues are treated with the same relevance throughout the entire paper.

Identifying Patients with Bacteremia in Community-Hospital Emergency Rooms: A Retrospective Cohort Study

Objectives

(1) To develop a clinical prediction rule to identify patients with bacteremia, using only information that is readily available in the emergency room (ER) of community hospitals, and (2) to test the validity of that rule with a separate, independent set of data.

Design

Multicenter retrospective cohort study.

Setting

To derive the clinical prediction rule we used data from 3 community hospitals in Japan (derivation). We tested the rule using data from one other community hospital (validation), which was not among the three “derivation” hospitals.

Participants

Adults (age ≥ 16 years old) who had undergone blood-culture testing while in the ER between April 2011 and March 2012. For the derivation data, n = 1515 (randomly sampled from 7026 patients), and for the validation data n = 467 (from 823 patients).

Analysis

We analyzed 28 candidate predictors of bacteremia, including demographic data, signs and symptoms, comorbid conditions, and basic laboratory data. Chi-square tests and multiple logistic regression were used to derive an integer risk score (the “ID-BactER” score). Sensitivity, specificity, likelihood ratios, and the area under the receiver operating characteristic curve (i.e., the AUC) were computed.

Results

There were 241 cases of bacteremia in the derivation data. Eleven candidate predictors were used in the ID-BactER score: age, chills, vomiting, mental status, temperature, systolic blood pressure, abdominal sign, white blood-cell count, platelets, blood urea nitrogen, and C-reactive protein. The AUCs was 0.80 (derivation) and 0.74 (validation). For ID-BactER scores ≥ 2, the sensitivities for derivation and validation data were 98% and 97%, and specificities were 20% and 14%, respectively.

Conclusions

The ID-BactER score can be computed from information that is readily available in the ERs of community hospitals. Future studies should focus on developing a score with a higher specificity while maintaining the desired sensitivity.

Multidisciplinary team review of best practices for collection and handling of blood cultures to determine effective interventions for increasing the yield of true-positive bacteremias, reducing contamination, and eliminating false-positive central line-associated bloodstream infections

BACKGROUND

A literature search was conducted using keywords for articles published in English from January 1990 to March 2015. Using criteria related to blood culture collection and handling, the search yielded 101 articles. References used also included Microbiology Laboratory standards, guidelines, and textbook information.

RESULTS

The literature identified diverse and complex issues surrounding blood culture practices, including the impact of false-positive results, laboratory definition of contamination, effect on central line-associated bloodstream infection (CLABSI) reporting, indications for collecting blood cultures, drawing from venipuncture sites versus intravascular catheters, selection of antiseptics, use of needleless connectors, inoculation of blood culture bottles, and optimizing program management in emergency departments, education, and implementation of bundled practice initiatives.

CONCLUSION

Hospitals should optimize best practice in the collection, handling, and management of blood culture specimens, an often overlooked but essential component in providing optimal care of patients in all settings and populations, reducing financial burdens, and increasing the accuracy of reportable CLABSI. Although universal concepts exist in blood culture practices, some issues require further research to determine benefit. Institutions undertaking a review of their blood culture programs are encouraged to use a checklist that addresses elements that encompass the research contained in this review.

Factors Associated with Blood Culture Contamination in the Emergency Department: Critical Illness, End-Stage Renal Disease, and Old Age

Background

Blood culture contamination in emergency departments (ED) that experience a high volume of patients has negative impacts on optimal patient care. It is therefore important to identify risk factors associated with blood culture contamination in EDs.

Methodology/Principal Findings

A prospectively observational study in a university-affiliated hospital were conducted between August 2011 and December 2012. Positive monomicrobial and negative blood cultures drawn from adult patients in the ED were analyzed to evaluate the possible risk factors for contamination. A total of 1,148 positive monomicrobial cases, 391 contamination cases, and 13,689 cases of negative blood culture were identified. Compared to patients with negative blood cultures, patients in triage levels 1 and 2 (Incidence Rate Ratio, IRR = 2.24), patients with end-stage renal disease (ESRD) (IRR = 2.05), and older patients (IRR: 1.02 per year) were more likely to be associated with ED blood culture contamination.

Conclusions/Significance

Critical patients (triage levels 1 and 2), ESRD patients, and older patients were more commonly associated with blood culture contamination in the ED. Further studies to evaluate whether the characteristics of skin commensals contribute to blood culture contamination is warranted, especially in hospitals populated with high-risk patients.

A risk prediction model for screening bacteremic patients: a cross sectional study

Background

Bacteraemia is a frequent and severe condition with a high mortality rate. Despite profound knowledge about the pre-test probability of bacteraemia, blood culture analysis often results in low rates of pathogen detection and therefore increasing diagnostic costs. To improve the cost-effectiveness of blood culture sampling, we computed a risk prediction model based on highly standardizable variables, with the ultimate goal to identify via an automated decision support tool patients with very low risk for bacteraemia.

Methods

In this retrospective hospital-wide cohort study evaluating 15,985 patients with suspected bacteraemia, 51 variables were assessed for their diagnostic potency. A derivation cohort (n = 14.699) was used for feature and model selection as well as for cut-off specification. Models were established using the A2DE classifier, a supervised Bayesian classifier. Two internally validated models were further evaluated by a validation cohort (n = 1,286).

Results

The proportion of neutrophile leukocytes in differential blood count was the best individual variable to predict bacteraemia (ROC-AUC: 0.694). Applying the A2DE classifier, two models, model 1 (20 variables) and model 2 (10 variables) were established with an area under the receiver operating characteristic curve (ROC-AUC) of 0.767 and 0.759, respectively. In the validation cohort, ROC-AUCs of 0.800 and 0.786 were achieved. Using predefined cut-off points, 16% and 12% of patients were allocated to the low risk group with a negative predictive value of more than 98.8%.

Conclusion

Applying the proposed models, more than ten percent of patients with suspected blood stream infection were identified having minimal risk for bacteraemia. Based on these data the application of this model as an automated decision support tool for physicians is conceivable leading to a potential increase in the cost-effectiveness of blood culture sampling. External prospective validation of the model's generalizability is needed for further appreciation of the usefulness of this tool.

Cost analysis of strategies to reduce blood culture contamination in the emergency department: sterile collection kits and phlebotomy teams

OBJECTIVE

Blood culture collection practices that reduce contamination, such as sterile blood culture collection kits and phlebotomy teams, increase up-front costs for collecting cultures but may lead to net savings by eliminating downstream costs associated with contamination. The study objective was to compare overall hospital costs associated with 3 collection strategies: usual care, sterile kits, and phlebotomy teams.

DESIGN

Cost analysis.

SETTING

This analysis was conducted from the perspective of a hospital leadership team selecting a blood culture collection strategy for an adult emergency department (ED) with 8,000 cultures drawn annually.

METHODS

Total hospital costs associated with 3 strategies were compared: (1) usual care, with nurses collecting cultures without a standardized protocol; (2) sterile kits, with nurses using a dedicated sterile collection kit; and (3) phlebotomy teams, with cultures collected by laboratory-based phlebotomists. In the base case, contamination rates associated with usual care, sterile kits, and phlebotomy teams were assumed to be 4.34%, 1.68%, and 1.10%, respectively. Total hospital costs included costs of collecting cultures and hospitalization costs according to culture results (negative, true positive, and contaminated).

RESULTS

Compared with usual care, annual net savings using the sterile kit and phlebotomy team strategies were $483,219 and $288,980, respectively. Both strategies remained less costly than usual care across a broad range of sensitivity analyses.

CONCLUSIONS

EDs with high blood culture contamination rates should strongly consider evidence-based strategies to reduce contamination. In addition to improving quality, implementing a sterile collection kit or phlebotomy team strategy is likely to result in net cost savings.

Blood culture contamination in hospitalized pediatric patients: a single institution experience

PURPOSE

Blood culture is the most important tool for detecting bacteremia in children with fever. However, blood culture contamination rates range from 0.6% to 6.0% in adults; rates for young children have been considered higher than these, although data are limited, especially in Korea. This study determined the contamination rate and risk factors in pediatric patients visiting the emergency room (ER) or being admitted to the ward.

METHODS

We conducted a retrospective chart review of blood cultures obtained from children who visited Yonsei Severance Hospital, Korea between 2006 and 2010. Positive blood cultures were labeled as true bacteremia or contamination according to Centers for Disease Control and Prevention/National Healthcare Safety Network definitions for laboratory-confirmed bloodstream infection, after exclusion of cultures drawn from preexisting central lines only.

RESULTS

Among 40,542 blood cultures, 610 were positive, of which 479 were contaminations and 131 were true bacteremia (overall contamination rate, 1.18%). The contamination rate in the ER was significantly higher than in the ward (1.32% vs. 0.66%, P<0.001). The rate was higher in younger children (2.07%, 0.94%, and 0.61% in children aged <1 year, 1-6 years, and >6 years, respectively).

CONCLUSION

Overall, contamination rates were higher in younger children than in older children, given the difficulty of performing blood sampling in younger children. The contamination rates from the ER were higher than those from the ward, not accounted for only by overcrowding and lack of experience among personnel collecting samples. Further study to investigate other factors affecting contamination should be required.

Reducing blood culture contamination in community hospital emergency departments: a multicenter evaluation of a quality improvement intervention

OBJECTIVES

Blood culture contamination is a common and preventable problem in the emergency department (ED). In a previous single-center study, changing the process of ED blood culture collection from the traditional "clean," nonsterile procedure to a fully sterile procedure with standardized use of sterile gloves, large-volume chlorhexidine skin antisepsis, and fenestrated sterile drapes resulted in a substantial reduction in contamination. The objective of the current study was to evaluate the effectiveness of this sterile blood culture collection process for reducing blood culture contamination in two community hospital EDs.

METHODS

The authors implemented the sterile blood culture collection process in the ED of two hospitals, including Hospital A, which historically had a contamination rate of approximately 5%, and Hospital B, with a 2.5% historical contamination rate. With an interrupted times-series design and segmented regression analysis to adjust for secular trends and autocorrelation, the monthly percentages of cultures contaminated at each hospital during an intervention period (sterile technique) were compared to a 10-month baseline period immediately preceding implementation (clean technique). At Hospital A, the full sterile blood culture collection process was used throughout the 16-month intervention period. At Hospital B, user feedback indicated poor adherence to the process due to difficulty implementing the fenestrated drape component; therefore, the process was simplified to the modified sterile collection process, in which the fenestrated drape component was dropped and sterile gloves and large-volume skin antisepsis were emphasized. Hence, at Hospital B, two intervention periods were compared to the baseline period: the 8-month intervention period 1 (full sterile process) and the subsequent 8-month intervention period 2 (modified sterile process).

RESULTS

At Hospital A, during the baseline period, 165 of 3,417 (4.83%) cultures were contaminated, while 142 of 5,238 (2.71%) were contaminated during the intervention period (p < 0.01). In the segmented regression model, the full sterile blood culture collection process was associated with an immediate 2.68% (95% confidence interval [CI] = 1.43% to 3.52%) absolute reduction in contamination and sustained reductions during the entire intervention period. At Hospital B, during the baseline, 63 of 2,509 (2.51%) cultures were contaminated. In intervention period 1 with the full sterile process, 51 of 1,865 (2.73%) cultures were contaminated (p = 0.65), with segmented regression results showing no changes compared to baseline. After simplification of the process to address poor adherence, the modified sterile process during intervention period 2 was associated with a significant reduction in contamination, with 17 of 1,860 (0.91%) cultures contaminated (p < 0.01 compared to baseline). The segmented regression model demonstrated the modified sterile process was associated with an immediate 1.53% (95% CI = 1.00% to 1.88%) absolute reduction in contamination with significant sustained reductions.

CONCLUSIONS

Changing the method of blood culture collection from the commonly used nonsterile technique to a sterile process resulted in significant reductions in blood culture contamination at two community hospital EDs, including one with low baseline contamination. Monitoring the implementation process at both sites was important to identify and overcome operational challenges. At one study site, simplification of the process by removing the fenestrated drape component was a key for successful implementation.

Reducing blood culture contamination in the emergency department: an interrupted time series quality improvement study

OBJECTIVES

Blood culture contamination is a common problem in the emergency department (ED) that leads to unnecessary patient morbidity and health care costs. The study objective was to develop and evaluate the effectiveness of a quality improvement (QI) intervention for reducing blood culture contamination in an ED.

METHODS

The authors developed a QI intervention to reduce blood culture contamination in the ED and then evaluated its effectiveness in a prospective interrupted times series study. The QI intervention involved changing the technique of blood culture specimen collection from the traditional clean procedure to a new sterile procedure, with standardized use of sterile gloves and a new materials kit containing a 2% chlorhexidine skin antisepsis device, a sterile fenestrated drape, a sterile needle, and a procedural checklist. The intervention was implemented in a university-affiliated ED and its effect on blood culture contamination evaluated by comparing the biweekly percentages of blood cultures contaminated during a 48-week baseline period (clean technique) and 48-week intervention period (sterile technique), using segmented regression analysis with adjustment for secular trends and first-order autocorrelation. The goal was to achieve and maintain a contamination rate below 3%.

RESULTS

During the baseline period, 321 of 7,389 (4.3%) cultures were contaminated, compared to 111 of 6,590 (1.7%) during the intervention period (p < 0.001). In the segmented regression model, the intervention was associated with an immediate 2.9% (95% confidence interval [CI] = 2.2% to 3.2%) absolute reduction in contamination. The contamination rate was maintained below 3% during each biweekly interval throughout the intervention period.

CONCLUSIONS

A QI assessment of ED blood culture contamination led to development of a targeted intervention to convert the process of blood culture collection from a clean to a fully sterile procedure. Implementation of this intervention led to an immediate and sustained reduction of contamination in an ED with a high baseline contamination rate.

Effectiveness of practices to reduce blood culture contamination: a Laboratory Medicine Best Practices systematic review and meta-analysis

OBJECTIVES

This article is a systematic review of the effectiveness of three practices for reducing blood culture contamination rates: venipuncture, phlebotomy teams, and prepackaged preparation/collection (prep) kits.

DESIGN AND METHODS

The CDC-funded Laboratory Medicine Best Practices Initiative systematic review methods for quality improvement practices were used.

RESULTS

Studies included as evidence were: 9 venipuncture (vs. versus intravenous catheter), 5 phlebotomy team; and 7 prep kit. All studies for venipuncture and phlebotomy teams favored these practices, with meta-analysis mean odds ratios for venipuncture of 2.69 and phlebotomy teams of 2.58. For prep kits 6 studies' effect sizes were not statistically significantly different from no effect (meta-analysis mean odds ratio 1.12).

CONCLUSIONS

Venipuncture and the use of phlebotomy teams are effective practices for reducing blood culture contamination rates in diverse hospital settings and are recommended as evidence-based "best practices" with high overall strength of evidence and substantial effect size ratings. No recommendation is made for or against prep kits based on uncertain improvement.

Blood cultures at central line insertion in the intensive care unit: comparison with peripheral venipuncture

Blood cultures are a key diagnostic test for intensive care unit (ICU) patients; however, contaminants complicate interpretations and lead to unnecessary antibiotic administration and costs. Indications for blood cultures and central venous catheter (CVC) insertions often overlap for ICU patients. Obtaining blood cultures under the strict sterile precautions utilized for CVC insertion might be expected to decrease culture contamination. This retrospective study compared the results of blood cultures taken at CVC insertion, at arterial line insertion, and from peripheral venipuncture in order to validate the advantage of CVC insertion cultures. Cultures from indwelling lines were excluded. Results of 14,589 blood cultures, including 2,736 (19%) CVC, 1,513 (10%) arterial line, and 10,340 (71%) peripheral cultures taken over 5.5 years in two ICUs (general and medical) were analyzed. CVC cultures were contaminated more frequently than arterial line or peripheral cultures (225/2,736 [8%] CVC, 48/1,513 [3%] arterial line, and 378/10,340 (4%) peripheral cultures [P < 0.001 for CVC versus peripheral and CVC versus arterial line cultures]). True pathogens were found more frequently in CVC insertion cultures (334/2,736 [12%] CVC, 155/1,513 [10%] arterial line, and 795/10,340 [8%] peripheral cultures [P < 0.001 for CVC versus peripheral cultures; P = 0.055 for CVC versus arterial line cultures; P < 0.001 for peripheral versus arterial line cultures]). Contamination and true-positive rates were similar for culture sets from the two ICUs for each given culture source. Despite superior sterile precautions, cultures taken at the time of central line insertion had a higher contamination rate than did either peripheral or arterial line blood cultures. This may be related to the increased manipulations required for CVC insertion.

Skin antiseptics in venous puncture-site disinfection for prevention of blood culture contamination: systematic review with meta-analysis

Blood cultures drawn by venous puncture are common clinical procedures for the detection of bacteraemia. Blood culture contamination (BCC) can lead to clinical misinterpretation and unnecessary expenses. We aimed to systematically review randomised controlled trials (RCTs) with skin antiseptics for prevention of contamination in venous-puncture drawn blood cultures. We conducted database search using CENTRAL (Cochrane Library issue April 2010), MEDLINE, EMBASE and mRCT, in June 2010. All RCTs testing skin antiseptics in venous-puncture drawn blood cultures were retrieved. Relative risk (RR) of the BCC outcome was analysed by random effects method using confidence interval (CI) of 95%. Studies were assessed by one review author and checked by another. Six studies were identified. Single-trial comparisons showed that alcoholic iodine tincture was better than non-alcoholic povidone-iodine, and isopropyl/acetone/povidone-iodine showed superiority against isopropyl/povidone-iodine. Meta-analysis demonstrated that alcoholic chlorhexidine was better than non-alcoholic povidone-iodine (RR: 0.33; 95% CI: 0.24-0.46) in 4757 blood cultures from two trials. Alcoholic solutions were better than non-alcoholic products (0.53; 0.31-0.90) in 21,300 blood cultures from four studies. Two trials with 13,418 blood cultures showed that iodine tincture was not superior to povidone-iodine in BCC prevention (0.79; 0.54-1.18). Alcoholic iodine was not different from non-alcoholic iodine (0.79; 0.53-1.17). Comparison of chlorhexidine vs iodine compounds was not conclusive. Alcohol alone was not inferior to iodinated products for prevention of contamination in venous-puncture drawn blood cultures. The association of alcohol and povidone-iodine did not seem to be useful. Alcoholic chlorhexidine solutions reduced blood culture false positives compared with aqueous povidone-iodine.

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.

Isopropyl alcohol compared with isopropyl alcohol plus povidone-iodine as skin preparation for prevention of blood culture contamination

Despite a number of studies on the efficacies of antiseptics for the prevention of blood culture contamination, it still remains unclear which antiseptic should be used. Although the combination of povidone-iodine and isopropyl alcohol has been traditionally used in many institutions, the application of povidone-iodine needs extra time, and there is little evidence that this combination could have an additive effect in reducing contamination rates. To elucidate the additive efficacy of povidone-iodine, we compared two antiseptics, 70% isopropyl alcohol only and 70% isopropyl alcohol plus povidone-iodine, in a prospective, nonrandomized, and partially blinded study in a community hospital in Japan between 1 October 2007 and 21 March 2008. All blood samples for culture were drawn by first-year residents who received formal training on collection techniques. Skin antisepsis was performed with 70% isopropyl alcohol plus povidone-iodine on all inpatient wards and with only 70% isopropyl alcohol in the emergency department. For the group of specimens from inpatient wards cultured, 13 (0.46%) of 2,797 cultures were considered contaminated. For the group of specimens from the emergency department cultured, 12 (0.42%) of 2,856 cultures were considered contaminated. There was no significant difference in the contamination rates between the two groups (relative risk, 0.90; 95% confidence interval, 0.41 to 1.98; P = 0.80). In conclusion, the use of a single application of 70% isopropyl alcohol is a sufficient and a more cost- and time-effective method of obtaining blood samples for culture than the use of a combination of isopropyl alcohol and povidone-iodine. The extremely low contamination rates in both groups suggest that the type of antiseptic used may not be as important as the use of proper technique.