R. Cartuyvels

The preanalytical optimization of blood cultures: a review and the clinical importance of benchmarking in 5 Belgian hospitals

Bloodstream infections remain a major challenge in medicine. Optimal detection of pathogens is only possible if the quality of preanalytical factors is thoroughly controlled. Since the laboratory is responsible for this preanalytical phase, the quality control of critical factors should be integrated in its quality control program. The numerous recommendations regarding blood culture collection contain controversies. Only an unambiguous guideline permits standardization and interlaboratory quality control. We present an evidence-based concise guideline of critical preanalytical determinants for blood culture collection and summarize key performance indicators with their concomitant target values. In an attempt to benchmark, we compared the true-positive rate, contamination rate, and collected blood volume of blood culture bottles in 5 Belgian hospital laboratories. The true-positive blood culture rate fell within previously defined acceptation criteria by Baron et al. (2005) in all 5 hospitals, whereas the contamination rate exceeded the target value in 4 locations. Most unexpected, in each of the 5 laboratories, more than one third of the blood culture bottles were incorrectly filled, irrespective of the manufacturer of the blood culture vials. As a consequence of this shortcoming, one manufacturer recently developed an automatic blood volume monitoring system. In conclusion, clear recommendations for standardized blood culture collection combined with quality control of critical factors of the preanalytical phase are essential for diagnostic blood culture improvement.

Timely diagnosis of respiratory tract infections: Evaluation of the performance of the Respifinder assay compared to the xTAG Respiratory Viral Panel assay

Abstract Background Respiratory tract infections are the most common cause of hospitalization in infants and young children and are typically caused by viral or, less commonly, bacterial pathogens. Existing non-molecular diagnostic methods have several drawbacks such as limited sensitivity, long turn-a-round time and limited number of pathogens that can be detected. Objectives Nucleic acid amplification methods can increase sensitivity and enable the initiation of appropriate interventions without delay. Broad-spectrum detection and identification circumvent the use of individual diagnostic DNA or RNA based assays. At present, several commercial assays are available for broad-spectrum detection. Study design We compared the performance of the xTAG Respiratory Viral Panel (RVP) (Luminex Molecular Diagnostics, Toronto, Canada) with that of the Respifinder (Pathofinder, Maastricht, Netherlands) for 9 external quality assurance (EQA) panels (QCMD, Scotland) consisting of a total of 106 EQA samples. Results Both the RVP and the Respifinder assay have an excellent specificity. Sensitivity was 33% and 78% for the RVP and the Respifinder assay, respectively. For both assays, sensitivity was low for weak positive samples. Discussion The results of our study seem to indicate a better sensitivity for the Respifinder. Analysis of patient samples is necessary to evaluate the clinical performance.

Performance of a New Chromogenic Medium, BBL CHROMagar MRSA II (BD), for Detection of Methicillin-Resistant Staphylococcus aureus in Screening Samples

ABSTRACT Two chromogenic media for the detection of MRSA were compared: BBL CHROMagar MRSA II (BD) and MRSA ID agar (bioMérieux). Following overnight nonselective enrichment, 1,919 screening samples were inoculated on both chromogenic agars. After 24 h, the sensitivities of both media were high and comparable. Both media showed an important decrease in specificity after 48 h of incubation (decreases of 8% for MRSA II and 10% for MRSA ID), but MRSA II was significantly more specific at both time points.

A hospital-level cost-effectiveness analysis model for toxigenic Clostridium difficile detection algorithms

BACKGROUND Despite thorough analyses of the analytical performance of Clostridium difficile tests and test algorithms, the financial impact at hospital level has not been well described. Such a model should take institution-specific variables into account, such as incidence, request behaviour and infection control policies. AIM To calculate the total hospital costs of different test algorithms, accounting for days on which infected patients with toxigenic strains were not isolated and therefore posed an infectious risk for new/secondary nosocomial infections. METHODS A mathematical algorithm was developed to gather the above parameters using data from seven Flemish hospital laboratories (Bilulu Microbiology Study Group) (number of tests, local prevalence and hospital hygiene measures). Measures of sensitivity and specificity for the evaluated tests were taken from the literature. List prices and costs of assays were provided by the manufacturer or the institutions. The calculated cost included reagent costs, personnel costs and the financial burden following due and undue isolations and antibiotic therapies. Five different test algorithms were compared. FINDINGS AND CONCLUSION A dynamic calculation model was constructed to evaluate the cost:benefit ratio of each algorithm for a set of institution- and time-dependent inputted variables (prevalence, cost fluctuations and test performances), making it possible to choose the most advantageous algorithm for its setting. A two-step test algorithm with concomitant glutamate dehydrogenase and toxin testing, followed by a rapid molecular assay was found to be the most cost-effective algorithm. This enabled resolution of almost all cases on the day of arrival, minimizing the number of unnecessary or missing isolations.

A Large Hospital Outbreak of Klebsiella pneumoniae (DHA-1 and SHV-11 Positive): Importance of Detection and Treatment of ampC β-Lactamases

Plasmid-borne ampC � -lactamases are emerging worldwide. There is no gold standard in detecting them so it is presumed their prevalence is underestimated. They may confer resistance to broad-spectrum cephalosporins. In this paper the first outbreak in Europe of a Klebsiella pneumoniae harbouring a plasmid-borne DHA-1 � -lactamase and a SHV-11 � - lactamase is reported. Following CLSI (Clinical Laboratories Standards Institute) guidelines the majority of isolates would have been reported susceptible to third generation cephalosporines in spite of increased MIC values. No failures were observed in patients treated with cefepime or meropenem. Infections were linked to stay on the intensive care unit and/or urological interventions. The outbreak was stopped after a meeting was organised between the department of infection control of the hospital and the complete ICU and urology staff in which the importance of strict hand hygiene to limit transmission was stressed.

Laboratory diagnosis of urinary tract infections: Towards a BILULU consensus guideline

Urinary tract infections (UTI) are very common throughout life and account for the majority of the workload in the clinical microbiology laboratory. Clear instructions for the interpretation of urine cultures by the laboratory technicians are indispensable to obtain standardized, reliable, and clinically useful results. In literature, there is often a lack of evidence-based practice in processing urinary samples in the laboratory. In this consensus document, the BILULU Study Group presents a practical approach for the implementation of existing guidelines for the culture of urine in the microbiology laboratory and offers answers for issues where no clear solution is available in the guidelines.

Establishing quality control ranges for temocillin following CLSI-M23-A3 guideline

Abstract Objectives: This study aimed to establish acceptable quality control ranges for temocillin disk diffusion tests and Etest® minimal inhibitory concentrations. Methods: According to Clinical and Laboratory Standards Institute (CLSI) guideline, a Tier 2 quality control study was performed and involves seven laboratories. Each of them tested 10 replicates of two quality control strains (Escherichia coli ATCC 25922 and E. coli ATCC 35218) on three different media lots and, for disk diffusion, two disk lots. Results: Proposed zone diameter quality control ranges were 12–25 mm for E. coli ATCC 25922 and 19–28 mm for E. coli ATCC 35218. Proposed Etest quality control ranges were 3–24 mg/l for E. coli ATCC 25922 and 2–6 mg/l E. coli ATCC 35218. Conclusion: Based on our results, we would advise the use of E. coli ATCC 35218 as QC strain for temocillin susceptibility testing and Etest because ranges obtained are narrower than with E. coli ATCC 25922 and do not overlap temocillin breakpoint.