Differential Time To Positivity Research Articles

Understanding the diagnosis of catheter-related bloodstream infection: real-time monitoring of biofilm growth dynamics using time-lapse optical microscopy.

The differential time to positivity (DTTP) technique is recommended for the conservative diagnosis of catheter-related bloodstream infection (C-RBSI). The technique is based on a 120-minute difference between microbial growth in blood drawn through the catheter and blood drawn through a peripheral vein. However, this cut-off has failed to confirm C-RBSI caused by Candida spp. and Staphylococcus aureus. We hypothesized that the biofilm of both microorganisms disperses faster than that of other microorganisms and that microbial load is rapidly equalized between catheter and peripheral blood. Therefore, our aim was to compare the biofilm dynamics of various microorganisms. Biofilm of ATCC strains of methicillin-resistant Staphylococcus epidermidis, methicillin-susceptible S. aureus, Enterococcus faecalis, Escherichia coli and Candida albicans was grown on silicon disks and analyzed using time-lapse optical microscopy. The time-lapse images of biofilms were processed using ImageJ2 software. Cell dispersal time and biofilm thickness were calculated. The mean (standard deviation) dispersal time in C. albicans and S. aureus biofilms was at least nearly 3 hours lower than in biofilm of S. epidermidis, and at least 15 minutes than in E. faecalis and E. coli biofilms. Our findings could explain why early dissemination of cells in C. albicans and S. aureus prevents us from confirming or ruling out the catheter as the source of the bloodstream infection using the cut-off of 120 minutes in the DTTP technique. In addition, DTTP may not be sufficiently reliable for E. coli since their dispersion time is less than the cut-off of 120 minutes.

Utility of Differential Time to Positivity in Diagnosing Central Line Associated Bloodstream Infections: A Systematic Review and Meta-Analysis.

Differential time to positivity (DTP), typically defined as pathogen growth at least two hours earlier from catheter vs paired peripheral blood cultures, is sometimes used to diagnose central line associated bloodstream infections (CLABSIs). Previous studies assessing DTP, however, have been small, provided conflicting results, and have not assessed heterogeneity across important subgroups. We conducted a systematic review of the diagnostic characteristics of DTP for CLABSI, using MEDLINE, Embase, Web of Science, CINAHL, LILACS, AMED and the Cochrane database. Studies were eligible for inclusion if they reported sensitivities, specificities, predictive values, likelihood ratios, or 2x2 tables of DTP for diagnosing CLABSI. Extracted data were analyzed by creating forest plots, performing bivariate model meta-analysis, and assessing quality using QUADAS-2. Our search identified 274 records of which 23 met criteria for meta-analysis. Among 2,526 suspected CLABSIs, DTP demonstrated a summary sensitivity of 81.3% (95% CI 72.8-87.7%), specificity of 91.8% (95% CI 84.5-95.8%), positive likelihood ratio of 9.89 (95% CI 5.14-19.00), and negative likelihood ratio of 0.20 (95% CI 0.14-0.30). Covariate analysis based on catheter duration, study design, and patient immune status demonstrated no significant differences. However, DTP performed worse for Staphylococcus aureus (low sensitivity but high specificity) and Candida (high sensitivity but low specificity) compared to other organisms. DTP performs well in ruling CLABSIs in or out. Obtaining paired catheter and peripheral blood cultures for DTP when the infectious source is unclear may prevent unnecessary line removal and diagnostic tests, although this needs to be balanced against potentially higher contamination rates from catheter cultures.

Usefulness of differential time to positivity between catheter and peripheral blood cultures for diagnosing catheter-related bloodstream infection: Data analysis from routine clinical practice in the intensive care unit

PurposeTo assess the accuracy of differential time to positivity (DTP) method for the diagnosis of catheter-related bloodstream infections (CRBSI) in the routine practice of our intensive care unit (ICU). Materials and methodsOver a five-year study period, ICU patients with a central venous catheter in place for ≥48 h and undergoing DTP test with catheter tip culture were analyzed. We investigated: the accuracy of DTP test with the usual threshold of 120 min in confirming the clinical suspicion of CRBSI; the most accurate threshold value of DTP to detect CRBSI; the diagnostic accuracy of the ratio (rather than the difference) between times to positivity. ResultsAmong 278 episodes of paired blood cultures, 13% were CRBSIs. DTP value ≥120 min used for the diagnosis of CRBSI yielded 41% sensitivity and 74% specificity. Performance of DTP values in predicting CRBSI was low (AUC = 0.60 [95%CI: 0.48–0.72]). Cutoff value of the ratio between times to positivity was 0.80, with 46% sensitivity and 79% specificity. ConclusionsThe routine use of the DTP method at any cutoff point has inadequate accuracy in detecting CRBSI in the real every day clinical practice. Not even the ratio between times to positivity seems to be clinically useful.

28 Blood culture collection practices in NICU; A national survey

Abstract Background Blood cultures are the gold standard in the investigation of neonatal sepsis, which is associated with significant morbidity and mortality. However, there are currently no consensus guidelines for blood collection for culture in newborns. In addition, it can be challenging to obtain sufficient blood volume in infants, which can affect the validity of culture results. Objectives To examine current practices in blood collection for culture in the investigation of neonatal sepsis in NICUs across Canada. Design/Methods A 9-item electronic survey (Appendix A) was sent to each of the 29 level 3 NICUs in Canada, which are equipped to provide highly specialized care for newborns. Results Responses were received from 26 (90%) of the 29 level 3 NICUs. Fifty-six percent of NICUs have blood collection guidelines for the investigation of neonatal sepsis. Forty-eight percent of NICUs routinely collect 1.0 mL of blood per culture bottle. By contrast, 32% of NICUs determine adequate blood volume using body weight and 8% using gestational age. In late-onset neonatal sepsis (LONS), 58% of centres process one aerobic culture bottle. Four NICUs (15%) routinely add anaerobic culture bottles. Few centres draw blood for culture from an indwelling catheter when present as a first-line option in LONS. Specifically, one NICU routinely draws blood from a central venous line and four NICUs (17%) routinely draw from a peripheral arterial line. In early-onset neonatal sepsis (EONS), 73% of NICUs draw blood for culture from umbilical lines, while 72% use peripheral venepuncture. Two centres routinely collect cord blood from the placenta for culture in EONS. Only one NICU applies the concept of differential time-to-positivity (DTP) in suspected central-line associated bloodstream infection (CLABSI) to determine whether a colonized catheter is the true source of infection. Conclusion There is significant practice variation in blood collection for culture in level 3 NICUs across Canada. Standardization of blood collection practices will improve antimicrobial stewardship and appropriate resource utilization, as well as provide reliable estimates of the true incidence of neonatal sepsis in Canada.

The comparative accuracy of pooled vs. individual blood culture sampling methods for diagnosis of catheter-related bloodstream infection

BackgroundCatheter-related bloodstream infection (CRBSI) is associated with increased morbidity, mortality, and cost of treatment in critically ill patients. A differential time to positivity (DTP) of 120 min or more between blood cultures obtained through the catheter vs. peripheral vein is an indicator of CRBSI with high sensitivity and specificity. However, it is no clear whether pooled sampling would be as efficient as individual sampling in order to reduce costs, contamination, or anemia.MethodsThis was a prospective diagnostic study conducted at the medical ICU and semi-ICU of Khon Kaen University’s Srinagarind Hospital in Thailand from May 2020 to November 2021. Fifty patients with triple-lumen central venous catheters (CVCs) who were clinically suspected of CRBSI were enrolled. 15 mL of blood was drawn through each catheter lumen, 10 mL of which was inoculated into three blood culture bottles, and the remaining 5 mL was pooled into a single bottle. Sensitivity, specificity, accuracy, and time to positivity of the pooled blood cultures were calculated using individual blood cultures as a reference.ResultsOf the 50 patients enrolled, 14 (28%) were diagnosed with CRBSI, 57.9% of whom were infected with gram-negative bacteria as the causative pathogen (57.9%). Extensively drug-resistant (XDR) Klebsiella pneumoniae was the most common organism. Sensitivity and specificity of the pooled blood sampling method were 69.23% (95% CI [0.44–0.94]) and 97.3% (95% CI [0.92–1.02]), respectively. The area under the ROC curve (AUC) was 0.83 (95% CI [0.68–0.99]). A paired T-Test to compare time to positivity of the pooled blood bottle and the first positive culture from the individual bottles indicated statistical significance (14.9 and 12.4 h, respectively). The mean difference was 2.5 [0.9–4.1] h, with a 95% CI and a p-value of 0.006.ConclusionPooled blood sampling results in a lower sensitivity and longer time to positivity for CRBSI diagnosis in patients with triple-lumen CVCs than individual lumen sampling.Trial registration Retrospectively registered at Thai Clinical Trials Registry. The study was reviewed and approved on 08/03/2022. TCTR identification number is TCTR20220308002

Role of Endoluminal Catheter Colonization Surveillance Cultures to Reduce Catheter-Related Blood Stream Infections in Hemodialysis Patients

Background: Central Venous Catheter (CVC) use as vascular access to the systemic circulation is highly vital for Hemodialysis (HD) patients. Catheter-related bloodstream infection (CRBSI) is the main complication of CVC use. Aim of the work: To assess the use of surveillance cultures (SCs) to prevent CRBSIs in asymptomatic HD patients. Patients and Methods: A prospective cohort study was conducted on eighteen HD patients with CVC, admitted to Dialysis Units of Benha University Hospitals and Meet Ghamr Nephrology and Urology Hospital during the period from October 2016 to March 2017. Endoluminal colonization of the catheter was assessed every 15 days by inoculating ~5 - 10 mL of endoluminal blood into aerobic blood culture bottles. Individual patients were triaged based on SC results: group 1 (negative); group 2 (coagulase-negative Staphylococcus [CoNS] with time-to-positivity (TTP) >14 hours); group 3 (CoNS with TTP ≤14 hours); and group 4 (any microorganism other than CoNS with any TTP or CoNS with Differential Time to Positivity (DTP) more than 120 minutes). Results: A total of 60 SCs were collected with a mean number per patient of 3.3. Of which 24 SCs (40%) were negative (group 1), and 36 SCs (60%) were positive (0 in group 2, 6 in group 3, and 30 in group 4). Under this protocol, the incidence density of CRBSI was 10.8 episodes per 1000 catheter days. Conclusion: SCs based on easily accessible samples proved useful in triaging HD patients at a high risk of infection.

Time to and differential time to blood culture positivity for assessing catheter-related yeast fungaemia: A longitudinal, 7-year study in a single university hospital.

Time to positivity (TTP) and differential time to positivity (DTTP) between central and peripheral blood cultures are commonly used for bacteraemia to evaluate the likelihood of central venous catheter (CVC)-related bloodstream infection. Few studies have addressed these approaches to yeast fungaemia. This study aimed to evaluate TTP and DTTP to assess CVC-related yeast fungaemia (CVC-RYF). We retrospectively analysed the results from 105 adult patients with incident fungaemia, with CVC removed and cultured, collected from 2010 to 2017. The bottles were incubated in a BioMérieux BacT/ALERT 3D and kept for at least 5days. Of the 105 patients included, most were oncology patients (85.7%) and had of long-term CVC (79.6%); 32 (30.5%) had a culture-positive CVC (defined as CVC-RYF) with the same species as in blood culture, and 69.5% had culture-negative CVC (defined as non-CVC-RYF, NCVC-RYF). Candida albicans represented 46% of the episodes. The median TTP was statistically different between CVC-RYF and NCVC-RYF (16.8hours interquartile range (IQR) [9.7-28.6] vs 29.4hours [IQR 20.7-41.3]; P=.001). A TTP <10hours had the best positive likelihood ratio (21.5) for CVC-RYF, although the sensitivity was only 28%. DTTP was available for 52 patients. A DTTP >5hours had a sensitivity of 100% and a specificity of 71% for CVC-RYF. Since the median TTP was 17hours and the most performing DTTP >5hours, these delays are too long to take a decision in the same operational day. More rapid methods for detecting infected catheters should be tested to avoid unnecessary CVC withdrawal.

Performance of differential time to positivity as a routine diagnostic test for catheter-related bloodstream infections: a single-centre experience

To assess the performance of differential time to positivity (DTP) for the diagnosis of catheter-related bloodstream infections (CRBSI). From all episodes of bloodstream infections (BSI) diagnosed during a 15-year period (2003-17) those in which a paired set of blood cultures drawn from a catheter and a peripheral vein were positive for the same microorganism and had a clinically and/or microbiologically defined source were selected. To assess diagnostic discrimination ability and accuracy of DTP for CRBSI, area under the receiver operating characteristic curves (AUC) and performance characteristics of a DTP ≥2h were computed. A total of 512 BSI were included, of which 302 (59%) were CRBSI. Discrimination ability of DTP was low for Staphylococcus aureus (AUC 0.656±0.06), coagulase-negative staphylococci (AUC 0.618±0.081), enterococci (AUC 0.554±0.117) and non-AmpC-producing Enterobacteriaceae (AUC 0.653±0.053); moderate for Pseudomonas aeruginosa (AUC 0.841±0.073), and high for AmpC-producing Enterobacteriaceae (AUC 0.944±0.039). For the entire sample, DTP had a low-to-moderate discrimination ability (AUC 0.698±0.024). A DTP ≥2h has a low sensitivity for coagulase-negative staphylococci (60%) and very low for S.aureus (34%), enterococci (40%) and non-AmpC-producing Enterobacteriaceae (42%). A DTP cut-off of 1h improved sensitivity (90%) for AmpC-producing Enterobacteriaceae. Differential time to positivity performs well for diagnosing CRBSI only when AmpC-producing Enterobacteriaceae and P.aeruginosa are involved. Performance is low for common Gram-positive organisms and non-AmpC-producing enteric bacilli; a negative test should not be used to rule out CRBSI due to these microorganisms. A DTP ≥1h may improve accuracy for AmpC-producing Enterobacteriaceae, particularly Enterobacter spp.

Comparison of semiquantitative and differential time to positivity methods for the diagnosis of central line-associated bloodstream infections in an intensive care unit

Introduction Central line-associated bloodstream infections (CLABSIs) adversely affect patients’ hospitalization.Aim We compared semiquantitative roll plate (SQRP) and differential time to positivity (DTP) culture methods in diagnosing CLABSIs.Methodology A retrospective study was conducted in an intensive care unit (ICU) from January 2013 to August 2014. All ICU patients with suspected CLABSIs were included. Blood cultures were taken, while central venous catheter (CVC) tips were cultured using the roll-tip method. DTP was considered positive if CVC lumen blood cultures became positive at least 2 h prior to concurrently drawn peripheral blood cultures with an identical micro-organism. SQRP method was considered positive when ≥15 c.f.u. of a micro-organism identical to that of blood cultures grew. Measures of diagnostic accuracy were calculated.Results SQRP displayed high sensitivity (94.7 %), while DTP showed high specificity (82.5 %). SQRP combined with DTP displayed 100 % sensitivity and negative predictive value.Conclusion SQRP and DTP methods should be evaluated in combination.

414. Diagnostic Usefulness of Differential Time to Positivity (DTP) in Neutropenic Cancer Patients With Suspected Catheter-Related Candidemia (CRC)

BackgroundThe decision of catheter removal in neutropenic patients with candidemia is difficult because they usually have surgically implanted catheter, and CRC are less frequent than in non-neutropenic patients. However, there are limited data on distinguishing CRC from non-CRC before catheter removal. We thus evaluated the diagnostic performances of DTP to diagnose CRC in neutropenic cancer patients with suspected CRC.MethodsAll adult neutropenic cancer patients with candidemia were enrolled in a tertiary care hospital from July 2012 to December 2016. Definite CRC was defined if ≥15 CFU of Candida spp. in a removed catheter tip. Probable CRC was defined if (1) one to 14 CFU in catheter tip, and clinical improvement within 48 hours after catheter removal with antifungal agent therapy or (2) the infection was refractory to antifungal therapy alone but improved within 48 hours after catheter removal. Non-CRC was defined if any of the following conditions were satisfied: (1) catheter tip cultures were negative and a noncatheter source of candidemia was found by culture, (2) the catheter tip cultures within 24 h before the start of antifungal therapy were negative, or (3) the clinical improvement before or without catheter removal. If the above conditions are not met, they were grouped into indeterminate, and were excluded from the final analysis. We defined the DTP as the difference in the time to positivity between blood cultures drawn simultaneously from the central vein and a peripheral vein.ResultsA total of 35 neutropenic patients with candidemia were enrolled. Of these, 15 patients (43%) with CRC (6 definite and nine probable) and 17 (48.5%) with non-CRC were finally analyzed, excluding threeindeterminate candidemia. On the basis of the receiver operating characteristics (ROC) curve, the optimal cut-off was ≥1.45 hours and the area under the ROC curve was 0.89 (95% CI, 76 to 100) in diagnosing CRC. Of the 15 patients with CRC, 11 (73%) revealed positive DTP, whereas none of the 17 patients with non-CRC exhibits positive DTP. The sensitivity and specificity of DTP for the diagnosis of CRC were 73% (95% CI, 58 to 94) and 100% (95% CI, 71 to 100), respectively.ConclusionDTP appears to be useful to rule in CRC and DTP ≥ 1.45 hours to be the optimal cut-off for CRC in neutropenic cancer patients.Disclosures All authors: No reported disclosures.

Clinical practice guidelines for the management of central venous catheter for critically ill patients

The objective of this article is to provide a guideline for the management of central venous catheter for critically ill patients. Electronic databases of CENTRAL, CINAHL, EMBASE, four Chinese databases (CBM, WANFANG DATA, CAJD, VIP Database) and Google Scholar were searched from inception to August 2017. The reviewers assessed each included study for the risk of bias under the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) framework. The GRADE evidence profile tables were added to each important clinical outcome. The guideline will be updated in a 5-year interval by incorporating new evidence. The guideline panel provided 11 statements on the management of central venous catheter for critically ill patients. Overall, there were 4 strong recommendations, and 7 weak recommendations. They were as follows: (I) we commend the use of catheter impregnation to prevent catheter-related blood stream infection (1A); (II) we suggest the use of real-time ultrasound guidance for subclavian or femoral vein insertion (2B), and recommend that for internal jugular vein (1A); (III) we suggest the use of real-time color Doppler ultrasound guidance on central venous catheterization for adult and pediatric patients (2C); (IV) we suggest not to use heparin for the maintenance of CVC patency (2A); (V) we suggest the use contrast-enhanced ultrasound for the confirmation of central venous catheter placement (2B); (VI) we recommend the use of bedside ultrasound together with agitated or non-agitated normal saline to confirm CVC position (1C); (VII) we suggest to use subclavian site for CVC insertion (2C); (VIII) we suggest not to use heparin-bonded catheters or warfarin to prevent CVC-related deep vein thrombosis in children (2D); (IX) we recommend the implementation of central-line bundles to reduce the risk of CRBSI for adult, pediatric and neonatal ICUs (1B); (X) we suggest skin antisepsis with chlorhexidine throughout in-dwelling period for reducing CVC-related infections (2D); (XI) we recommend a differential time to positivity (DTP) of blood cultures from CVC and peripheral vein of 120 minutes to diagnose CRBSI (1B). Substantial agreement exists among experts for issuing strong recommendations for the management of central venous catheter. Although a significant number of aspects of care have relatively weak support, evidence-based recommendations regarding the management of central venous catheter are the foundation of improved outcomes for critically ill patients.

Central venous catheter-related bloodstream infections (CVC-BSI) in patients of clinically suspected septicemia.

Central venous catheter-related bloodstream infections (CVC-BSI) are associated with morbidity and mortality especially in critically ill patients. This study was performed to find out the rate of CVC-BSI and CVC colonization, causative organism and their antibiogram in patients of Intensive Care Unit (ICU) and Department of Nephrology of tertiary care hospitals. A total of 100 patients from Bangabandhu Sheikh Mujib Medical University (BSMMU) and Dhaka Medical College Hospital (DMCH) who had-CVC and clinically suspected of septicemia were included in the study. Paired CVC blood and peripheral venous blood (PVB) samples were collected from each patient and were cultured by automated blood culture method. CVC-BSI was diagnosed in 11% and CVC colonization in 43% patients by Differential time to positivity (DTP) method. Rate of CVC-BSI was 8/1000 CVC days and 11/1000 CVC days in BSMMU and DMCH respectively whereas CVC colonization rate was 32/1000 CVC days and 47.5/1000 CVC days in BSMMU and DMCH. The most common bacteria causing CVC-BSI was Klebsiella spp. (36.4%) followed by Acinetobacter spp. (27.3%), Pseudomonas spp. (18.2%) and E. coli (18.2%). Among bacteria isolated from CVC colonization majority were Pseudomonas spp. (30.23%) and Staphylococcus epidermidis (30.23%) followed by Acinetobacter spp. (27.91%), Enterococcus spp. (6.98%). Most of the isolated bacteria causing CVC-BSI were resistant to commonly used antibiotics, but showed good sensitivity to imipenem and colistin. Information about CVC-BSI, -colonization and antibiogram of this study can help to guide the selection of suitable antibiotics for empirical therapy and to improve infection control measures of the hospital.

The value of differential time to positivity of blood cultures in diagnosis of catheter-related bloodstream infection in patients with solid tumors in intensive care unit

To determine the value of differential time to positivity (DTTP) of blood culture for the diagnosis of catheter-related bloodstream infection (CRBSI) in patients with solid tumors in intensive care unit (ICU). A retrospective study was conducted. 615 pairs of peripheral vein blood cultures and instantaneous catheter tip blood culture of 615 patients admitted to ICU of Tianjin Medical University Cancer Institute and Hospital were collected from August 2011 to March 2014. The DTTP method and (or) semi quantitative culture of catheter tip were compared. CRBSI was diagnosed when both cultures were positive for the same microorganism and DTTP≥2 hours (120 minutes). The result of this procedure was compared with that of organism obtained using the semi quantitative culture of blood at catheter tip with ≥15 cfu. Based on the clinical diagnosis, the reliability of two kinds of laboratory examination was compared for the diagnosis of CRBSI by plotting receiver operator characteristic curve (ROC curve). The result of 615 cases suspected of having CRBSI were analyzed during the study period. Of these, 440 episodes were excluded because cultures were negative for blood obtained through peripheral vein and central vein. Eight episodes were excluded because only peripheral vein blood culture was positive and 57 episodes were excluded because of only central vein blood culture was positive, 68 pairs of blood cultures were excluded due to the presence of multiple catheters and repeated blood withdrawals. Two cases of polymicrobial cultures were excluded from the final analysis due to the difficulty in determining the time of positive result for each individual microorganism. Ten cases in 42 cases of suspected cases of CRBSI were excluded from analysis because catheter was not removed, therefore culture from catheter tip could not be obtained. Using the DTTP method, 14 out of 17 CRBSI cases were diagnosed with DTTP≥120 minutes, while 3 cases were missed; the semi quantitative catheter tip culture was positive in 13 cases, and in 4 cases it was neglected. In 2 cases of CRBSI it was missed by both methods. The area under the ROC curve (AUC) of DTTP, catheter tip culture and the combination method was 0.912, 0.882 and 0.941 for diagnosis of CRBSI, respectively. Validity values for the diagnosis of CRBSI for DTTP were: sensitivity 82.35%, specificity 92.31%, positive predictive value 93.33% and negative predictive value 80.00%, and they were higher than those of the catheter tip culture method only (76.47%, 84.62%, 86.67% and 73.33%). The specificity and positive predictive CRBSI combination of the two methods in the diagnosis value were up to 100%, the sensitivity (88.24%) and negative predictive value (86.67%) was also increased, but no significant differences were found with DTTP method (χ2=0.00, P=1.00; χ2=0.00, P=0.98; χ2=0.00, P=0.98; χ2=0.00, P=0.98). DTTP can be a valid method recommended for CRBSI diagnosis in critically ill patients with acceptable sensitivity, good specificity as well as positive predictive value. DTTP combined with other clinical symptoms can not only avoid unnecessary catheter withdrawal, but it also can help obtain the optimal treatment time and strategy.

Evaluating Approaches for the Diagnosis of Hemodialysis Catheter-Related Bloodstream Infections.

Guideline-recommended diagnostic criteria for hemodialysis (HD) catheter-related bloodstream infections (CRBSIs) are based on data from indwelling central catheters in patients not on HD and non-HD situations, and upon which peripheral vein cultures are the gold standard. We aimed to examine the validity of these criteria in patients on HD. Adult patients on in-center HD using catheters were prospectively followed from 2011 to 2014 at a large academic-based HD facility (Toronto, Canada). When a CRBSI was suspected, blood culture sets were obtained from four sites (peripheral vein, both catheter hubs, and HD circuit) to determine the guideline-recommended differential time to positivity (DTTP). DTTP criteria were met when catheter hub cultures turned positive ≥120 minutes before peripheral vein cultures. The sensitivity, specificity, and accuracy were first calculated using peripheral vein cultures as the gold standard and then these same calculations were repeated with additional information, including exit site/catheter tip and HD circuit cultures, as the true gold standard. The feasibility of obtaining peripheral vein cultures was determined. Of 178 suspected CRBSIs, 100 had peripheral vein blood cultures. Using the true gold standard, sensitivity, specificity, and accuracy of blood culture results were highest in samples from the HD circuit (93.5%, 100%, and 95%, respectively). The guideline recommended combination of peripheral vein and arterial hub blood cultures was the least sensitive, specific, and accurate (91.7%, 93.1%, and 92.7%, respectively). The diagnostic criteria using measured DTTP were met in less than one third of events. In patients on HD, blood culture results are the most sensitive, specific, and accurate for diagnosing CRBSIs when taken from the HD circuit and the venous catheter hub, and blood culture results are the least sensitive, specific, and accurate in any combination with peripheral vein cultures. The DTTP does not increase diagnostic accuracy, reducing the necessity for venipuncture and its potential vein damage. Future guidelines should consider the applicability of criterion on specific patient populations and tailor them accordingly.

In situ diagnostic methods for catheter related bloodstream infection in burns patients: A pilot study

BackgroundOne of the most common and potentially fatal complications in critically ill burns patients is catheter related bloodstream infection (CR-BSI). Lack of in situ diagnostic techniques requires device removal if CR-BSI is suspected with 75–85% of catheters withdrawn unnecessarily. AimsTo assess the sensitivity, specificity and accuracy of two in situ diagnostic methods for CR-BSI in an adult ICU burns population: Differential Time to Positivity (DTP) and Semi-Quantitative Superficial Cultures (SQSC). MethodsBoth arterial (AC) and central venous (CVC) catheters were studied. On clinicians’ suspicion of CR-BSI, the CVC and AC were removed. Superficial semi-quantitative cultures were taken by removing the dressings and swabbing within a 3cm radius of the CVC and AC insertion sites, as well as inside each hub of the CVC and AC. Peripheral blood was taken for qualitative culture and the catheter tip sent for semi-quantitative culture. DTP was considered positive if culture of lumen blood became positive at least 120min before peripheral blood with an identical pathogen. Superficial and tip cultures were identified as positive if ≥15 CFUs were grown. CR-BSI was confirmed when both catheter tip culture and peripheral blood culture were positive with the same micro-organism. ResultsSixteen patients (88% male) with an APACHE II score of 22.0 (7.3) were enrolled. The mean age was 45.7 (16.9) years with mean total burn surface area 32.9 (19.4)%. Fifty percent had airway burns. ICU stay was 19.9 (11.1) days. All 16 survived ICU discharge with a hospital survival of 93%. There were 20 episodes of CR-BSI in these 16 patients. For these 20 episodes the exposure time (line days) was 113.15. The CR-BSI rate was 15.6 per 1000 catheter days (95% CI 1.9–56.4). For diagnosis of CR-BSI in either AC and CVC, SQSC had a sensitivity of 50% [95% CI 3–97], specificity 83.3% [95% CI 67–93], PPV 14.3 [95% CI 1–58], NPV 96.8 [95% CI 81–100], accuracy of 81.6% [95%CI 65–92] and diagnostic odds ratio 5.0 [95% CI 0.3–91.5]. To diagnose tip colonisation (>15CFU), sensitivity of SQSC was 75% [95% CI 22–99], specificity 88.2% [95%CI 72–96], PPV 42.7 [95% CI 12–80], NPV96.8% [95% CI 81–100], accuracy 86.8% [95% CI 71–95] and diagnostic odds ratio 22.5 [95% CI 1.9–271.9]. For combined DTP blood cultures, sensitivity for CR-BSI was 50% [95% CI 3–97], with specificity 97% [95% CI 82–100], PPV 50% [5% CI 3–97%], NPV 97% [95% CI 82–100], accuracy 94.3% 95% CI 79–99] and diagnostic odds ratio 32 [95% CI 1.1–970.8]. ConclusionBoth DTP and SQSC displayed high specificity, NPV and accuracy in a population of adult burns patients. These features may make these tests useful for ruling out CR-BSI in this patient group. This study was limited by a low number of events and further research is required.

Blood culture differential time to positivity enables safe catheter retention in suspected catheter-related bloodstream infection: a randomized controlled trial

ObjectiveTo evaluate the clinical usefulness and safety of the differential-time-to-positivity (DTP) method for managing the suspicion of catheter-related bloodstream infection (CR-BSI) in comparison with a standard method that includes catheter removal in critically ill patients. Methods-DesignA prospective randomized study was carried out. Setting: A 16-bed clinical-surgical ICU (July 2007-February 2009). Interventions: Patients were randomly assigned to one of two groups at the time CR-BSI was suspected. In the standard group, a standard strategy requiring catheter withdrawal was used to confirm or rule out CR-BSI. In the DTP group, DTP without catheter withdrawal was used to confirm or rule out CR-BSI. Measurements: clinical and microbiological data, CR-BSI rates, unnecessary catheter removals, and complications due to new puncture or to delays in catheter removal. ResultsTwenty-six patients were analyzed in each group. In the standard group, 6 of 37 suspected episodes of CR-BSI were confirmed and 5 colonizations were diagnosed. In the DTP group, 5 of 26 suspected episodes of CR-BSI were confirmed and four colonizations were diagnosed. In the standard group, all catheters (58/58, 100%) were removed at the time CR-BSA was suspected, whereas in the DTP group, only 13 catheters (13/41, 32%) were removed at diagnosis, and 10 due to persistent septic signs (10/41, 24%). In cases of confirmed CR-BSI, there were no differences between the two groups in the evolution of inflammatory parameters during the 48hours following the suspicion of CR-BSI. ConclusionsIn critically ill patients with suspected CR-BSI, the DTP method makes it possible to keep the central venous catheter in place safely.

The application of time to positivity in blood culture

Time to positivity (TTP) is a new parameter in blood culture field. The article shows us the concepts of TTP, differential time to positivity (DTTP), and introduces their relation with bloodstream infection (BSI), catheter-related bloodstream infection (CRBSI). Besides, it stresses TTP′s clinical application, including determining the severity of disease; identifying the isolates whether pollution or not; identification of isolate strains; detection of the drug resistance of isolates; evaluating the effect of antibiotic; helping to adjust the therapeutic drug; diagnosing or excluding CRBSI by means of DTTP; deciding whether the catheter is the source of infection in patients with candidemia; understanding the epidemiological distribution of strain. At the same time, the article also describes the shortcomings and domestic current status. (Chin J Lab Med, 2015, 38: 67-69) Key words: Sepsis; Colong count, microbiol; Microbiological techniques

Differential Time to Positivity for Catheter-Related Candidemia

Differential time to positivity (DTP) — the difference in time to positivity between blood cultures drawn simultaneously from a central venous catheter

Diagnostic Usefulness of Differential Time to Positivity for Catheter-Related Candidemia

A differential time to positivity (DTP) of ≥ 120 min is useful for diagnosing catheter-related bacteremia, but data on diagnosing catheter-related candidemia (CRC) in this way are limited. We wished to evaluate the usefulness of the DTP for diagnosing CRC. All adult patients who had the same Candida species isolated from blood cultures drawn simultaneously from a central venous catheter (CVC) and a peripheral vein were included at a tertiary care hospital over an 18-month period. A total of 105 patients with candidemia who had positive simultaneous CVC and peripheral vein blood cultures were included in our study. Sixty-one patients (58%) had CRC (47 definite and 14 probable), and 38 (36%) had candidemia from another source (non-CRC). The remaining 6 patients (6%) with indeterminate candidemia were excluded from the final analysis. The overall sensitivity and specificity of a DTP of ≥ 120 min for diagnosing CRC were 85% (95% confidence interval [CI], 74% to 93%) and 82% (95% CI, 66% to 92%), respectively, and for neutropenic patients, they were 75% (95% CI, 19% to 99%) and 100% (95% CI, 75% to 100%), respectively. For Candida glabrata infections, the optimal DTP cutoff was ≥ 6 h, with a sensitivity of 63% (95% CI, 35% to 85%) and a specificity of 75% (95% CI, 35% to 97%). In summary, DTP is useful for diagnosing CRC, and a DTP of ≥ 120 min appears to be the optimal cutoff except for CRC caused by C. glabrata. For neutropenic patients, DTP may be useful as an adjunct test to rule in CRC and to decide whether a catheter should be removed.

Blood culture differential time to positivity enables safe catheter retention in suspected catheter-related bloodstream infection: a randomized controlled trial

ObjectiveTo evaluate the clinical usefulness and safety of the differential-time-to-positivity (DTP) method for managing the suspicion of catheter-related bloodstream infection (CR-BSI) in comparison with a standard method that includes catheter removal in critically ill patients. Methods-DesignA prospective randomized study was carried out. Setting: A 16-bed clinical-surgical ICU (July 2007-February 2009). Interventions: Patients were randomly assigned to one of two groups at the time CR-BSI was suspected. In the standard group, a standard strategy requiring catheter withdrawal was used to confirm or rule out CR-BSI. In the DTP group, DTP without catheter withdrawal was used to confirm or rule out CR-BSI. Measurements: clinical and microbiological data, CR-BSI rates, unnecessary catheter removals, and complications due to new puncture or to delays in catheter removal. ResultsTwenty-six patients were analyzed in each group. In the standard group, 6 of 37 suspected episodes of CR-BSI were confirmed and 5 colonizations were diagnosed. In the DTP group, 5 of 26 suspected episodes of CR-BSI were confirmed and four colonizations were diagnosed. In the standard group, all catheters (58/58, 100%) were removed at the time CR-BSA was suspected, whereas in the DTP group, only 13 catheters (13/41, 32%) were removed at diagnosis, and 10 due to persistent septic signs (10/41, 24%). In cases of confirmed CR-BSI, there were no differences between the two groups in the evolution of inflammatory parameters during the 48hours following the suspicion of CR-BSI. ConclusionsIn critically ill patients with suspected CR-BSI, the DTP method makes it possible to keep the central venous catheter in place safely.