scholarly journals Assessment of a Multiplex LAMP Assay (Eazyplex® CSF Direct M) for Rapid Molecular Diagnosis of Bacterial Meningitis: Accuracy and Pitfalls

2021 ◽  
Vol 9 (9) ◽  
pp. 1859
Author(s):  
Anne-Gaëlle Leroy ◽  
Elise Persyn ◽  
Sophie-Anne Gibaud ◽  
Lise Crémet ◽  
Paul Le Turnier ◽  
...  
Keyword(s):  
Antibiotic Therapy ◽  
Lumbar Puncture ◽  
False Negative ◽  
Lamp Assay ◽  
Predictive Values ◽  
Amplification Curve ◽  
E Coli ◽  
Negative Results ◽  
False Negative Results ◽  
Automated Software

Background: Automated molecular panels are attractive tools for improving early meningitis diagnosis. This study assessed the Eazyplex® CSF direct M panel (EP), a multiplex real-time Loop-Mediated Isothermal Amplification assay. Methods: From December 2016 to December 2019, cerebrospinal fluid (CSF) samples were routinely tested with the EP V1.0. CSF parameters and microbiological and clinical data were retrospectively collected. Results: Out of 230 CSF samples, the EP yielded positive, negative, and invalid results for 32 (13.9%) (16 N. meningitidis, nine S. pneumoniae, two S. agalactiae, two E. coli, two H. influenzae, one L. monocytogenes), 182 (79.1%), and 16 (7%) samples, respectively. Among the positive samples, 14 (44%) remained negative in culture (antibiotic therapy before lumbar puncture (n = 11), meningococcal meningitis (n = 3)). High CSF protein concentrations and cellularity were associated with LAMP inhibition, counteracted by centrifugation. The automated software yielded 13 false positive and five false negative results. Amplification curve analysis was necessary and enabled the attainment of positive (PPA) and negative percentage agreement and positive and negative predictive values of 91.4%, 100%, 100%, and 98.3%. Three false negative results remained (two E. coli and one N. meningitidis). E. coli presented the poorest PPA (50%). Conclusion: This work confirms the strong performance of the EP, of particular interest in cases of antibiotic therapy before lumbar puncture.

scholarly journals PCR and Blood Culture for Detection ofEscherichia coli Bacteremia in Rats

1999 ◽  
Vol 37 (8) ◽  
pp. 2479-2482 ◽  
Author(s):  
Alexandra Heininger ◽  
Marlies Binder ◽  
Sibylle Schmidt ◽  
Klaus Unertl ◽  
Konrad Botzenhart ◽  
...  
Keyword(s):  
Blood Culture ◽  
Detection Rate ◽  
False Negative ◽  
Diagnostic Procedures ◽  
Microbial Pathogens ◽  
Gene Encoding ◽  
E Coli ◽  
Negative Results ◽  
False Negative Results ◽  
Male Wistar Rats

Critically ill patients often develop symptoms of sepsis and therefore require microbiological tests for bacteremia that use conventional blood culture (BC) techniques. However, since these patients frequently receive early empirical antibiotic therapy before diagnostic procedures are completed, examination by BC can return false-negative results. We therefore hypothesized that PCR could improve the rate of detection of microbial pathogens over that of BC. To test this hypothesis, male Wistar rats were challenged intravenously with 106 CFU of Escherichia coli. Blood was then taken at several time points for detection of E. coliby BC and by PCR with E. coli-specific primers derived from the uidA gene, encoding β-glucuronidase. In further experiments, cefotaxime (100 or 50 mg/kg of body weight) was administered intravenously to rats 10 min after E. colichallenge. Without this chemotherapy, the E. coli detection rate decreased at 15 min and at 210 min after challenge from 100% to 62% of the animals with PCR and from 100% to 54% of the animals with BC (P, >0.05). Chemotherapy decreased the E. coli detection rate at 25 min and at 55 min after challenge from 100% to 50% with PCR and from 100% to 0% with BC (P, <0.05). Thus, at clinically relevant serum antibiotic levels, PCR affords a significantly higher detection rate than BC in this rat model. The results suggest that PCR could be a useful adjunct tool supplementing conventional BC techniques in diagnosing bacteremia.

scholarly journals Contrast of Real-Time Fluorescent PCR Methods for Detection of Escherichia coli O157:H7 and of Introducing an Internal Amplification Control

2019 ◽  
Vol 7 (8) ◽  
pp. 230 ◽  
Author(s):  
Zhao ◽  
Xia ◽  
Liu
Keyword(s):  
Real Time ◽  
Water Samples ◽  
False Negative ◽  
Internal Amplification Control ◽  
Pcr Assay ◽  
The Real ◽  
E Coli ◽  
Negative Results ◽  
False Negative Results ◽  
Fluorescent Pcr

Various constituents in food specimens can inhibit the PCR assay and lead to false-negative results. An internal amplification control was employed to monitor the presence of false-negative results in PCR amplification. In this study, the objectives were to compare the real-time PCR-based method by introducing a competitive internal amplification control (IAC) for the detection of Escherichia O157:H7 with respect to the specificity of the primers and probes, analytical sensitivity, and detection limits of contamination-simulated drinking water. Additionally, we optimized the real-time fluorescent PCR detection system for E. coli O157:H7. The specificity of primers and probes designed for the rfbE gene was evaluated using four kinds of bacterial strains, including E. coli O157:H7, Staphylococcus aureus, Salmonella and Listeria monocytogenes strains. The real time PCR assay unambiguously distinguished the E. coli O157:H7 strains after 16 cycles. Simultaneously, the lowest detection limit for E. coli O157:H7 in water samples introducing the IAC was 104 CFU/mL. The analytical sensitivity in water samples had no influence on the detection limit compared with that of pure cultures. The inclusion of an internal amplification control in the real-time PCR assay presented a positive IAC amplification signal in artificially simulated water samples. These results indicated that real-time fluorescent PCR combined with the IAC possessed good characteristics of stability, sensitivity, and specificity. Consequently, the adjusted methods have the potential to support the fast and sensitive detection of E. coli O157:H7, enabling accurate quantification and preventing false negative results in E. coli O157:H7 contaminated samples.

scholarly journals Characterization of Focal Liver Lesions using CEUS and MRI with Liver-Specific Contrast Media: Experience of a Single Radiologic Center

2017 ◽  
Vol 38 (06) ◽  
pp. 619-625 ◽  
Author(s):  
Lukas Beyer ◽  
Florian Wassermann ◽  
Benedikt Pregler ◽  
Katharina Michalik ◽  
Janine Rennert ◽  
...  
Keyword(s):  
Contrast Media ◽  
Predictive Value ◽  
False Negative ◽  
Focal Liver Lesions ◽  
Liver Lesions ◽  
Predictive Values ◽  
Negative Results ◽  
False Negative Results ◽  
Sensitivity Specificity

Abstract Aim The purpose of this study was to compare contrast-enhanced ultrasound (CEUS), magnetic resonance imaging (MRI) using liver-specific contrast agent and a combination of both for the characterization of focal liver lesions (FLL). Methods 83 patients with both benign and malignant liver lesions were examined using CEUS and MRI after the intravenous administration of liver-specific contrast media. All patients had inconclusive results from prior imaging examinations. Histopathological specimens could be obtained in 53 patients. Ultrasound was performed using a multi-frequency curved probe (1 – 6 MHz) after the injection of 1 – 2.4 ml ultrasound contrast media. The sensitivity, specificity, positive predictive value and negative predictive value of CEUS, MRI and a combination of both (CEUS + MRI) were compared. Results The sensitivity, specificity, positive and negative predictive values regarding lesion classification were 90.9 %, 70.6 %, 92.3 % and 66.6 %, respectively, for CEUS; 90.9 %, 82.4 %, 95.2 % and 70.0 %, respectively, for MRI; and 96.9 %, 70.6 %, 92.7 % and 85.7 % respectively, for CEUS + MRI. There were no statistically significant differences. 6 malignant lesions were missed using CEUS or MRI alone (false negatives). The use of both modalities combined reduced the false-negative results to 2. Conclusion CEUS and MRI with liver-specific contrast media are very reliable and of equal informative value in the characterization of focal liver lesions. The number of false-negative results can be decreased using a combination of the two methods.

Cerebrospinal fluid vasopressin as a marker of central nervous system metastases from small-cell bronchogenic carcinoma.

1985 ◽  
Vol 3 (1) ◽  
pp. 48-53 ◽  
Author(s):  
A G Pedersen ◽  
M Hammer ◽  
M Hansen ◽  
P S Sørensen
Keyword(s):  
Bronchogenic Carcinoma ◽  
False Negative ◽  
Leptomeningeal Carcinomatosis ◽  
Small Cell ◽  
Cns Metastases ◽  
Predictive Values ◽  
Computed Tomographic ◽  
Negative Results ◽  
False Negative Results ◽  
Small Cell Bronchogenic Carcinoma

Vasopressin (ADH) was measured in CSF and plasma in 75 evaluable patients with known or suspected CNS metastases from small-cell bronchogenic carcinoma (SCBC), and in 66 control patients having neither malignant disease nor organic CNS disease. The presence of CNS metastases was confirmed or excluded on the basis of computed tomographic scans, neurologic examination, and autopsy. Twenty-four of the 75 patients had no CNS metastases. Ten of the 51 patients with CNS metastases had leptomeningeal carcinomatosis (MC). CSF-ADH was significantly increased in patients with MC (P less than .05), but not in patients having exclusively parenchymatous CNS metastases. Taking 2 pg/mL (95th percentile of control patients) as the upper limit of normal, 15 SCBC patients had elevated CSF-ADH, including 12 patients with CNS metastases and six patients with MC. The CSF-ADH to plasma ADH ratio was significantly increased in patients with CNS metastases (P less than .05). Patients without CNS metastases had a ratio less than or equal to 0.8 whereas the ratio was greater than 0.8, in 21 of the 51 patients with CNS metastases. The positive and negative predictive values with 95% confidence limits were 84% to 100% and 31% to 59%, respectively. Patients with inappropriate secretion of ADH (SIADH) constituted a significantly greater proportion of patients with elevated CSF-ADH than of patients with normal CSF-ADH levels (P less than .05). In addition, patients with SIADH constituted a significantly greater proportion of patients with MC than of patients with parenchymatous metastases (P less than .05). The diagnostic application of these findings is limited because of the large number of false-negative results, but it may prove to be of value in conjunction with the measurement of other tumor markers.

scholarly journals 408. Evaluation of the negative predictive value of the SARS-CoV-2 PCR respiratory assays in asymptomatic children undergoing surgery

2020 ◽  
Vol 7 (Supplement_1) ◽  
pp. S272-S272
Author(s):  
Suchitra Rao ◽  
Lilliam Ambroggio ◽  
Edwin J Asturias ◽  
Lalit Bajaj ◽  
Michelle Corrado ◽  
...  
Keyword(s):  
High Risk ◽  
False Negative ◽  
Tracheal Aspirate ◽  
Sample Type ◽  
Predictive Values ◽  
Test Characteristics ◽  
Negative Results ◽  
Paired Samples ◽  
Asymptomatic Children ◽  
False Negative Results

Abstract Background Universal pre-operative screening with SARS-CoV-2 PCR has been adopted by institutions to mitigate risk to healthcare workers (HCW) during aerosol-generating procedures such as intubation. However, there remains uncertainty regarding rates of false negative results and optimal sampling type. The objective was to determine the reliability of single, pre-operative SARS-CoV-2 testing from the nasopharynx in children undergoing general anesthesia. Methods Children &lt; 18 years of age who underwent intubation for a procedure received pre-operative testing 24–48 hours prior with a nasopharyngeal (NP) swab or wash, in conjunction with intra-operative nasal wash (NW) and tracheal aspirate (TA) sampling. All paired samples underwent testing using the Simplexa DiaSorin platform or a modified Centers for Disease Control assay. Cohen’s Kappa was used for interrater reliability of each sample result. McNemar’s Test was used to compare result proportions by sample type. Positive and negative predictive values (PPV, NPV) were calculated based on the intraoperative NW as the reference standard. Analyses were conducted using SAS (v 9.4). Results We collected full sample sets from 364 children from April 14 to May 15; 66% of pre-operative samples were NP swabs. The median age was 6 years (IQR 2,13), 55% were male, 68% were white and 41% of children had a high-risk comorbidity. Most surgeries were conducted by general surgery (23%), followed by orthopedics (19%). Only 2.5% of children had respiratory symptoms, and 4.8% had a documented fever within a week of the procedure. SARS-CoV-2 positive samples occurred in 4/364 (1%) of pre-operative samples, 8/363 (2.2%) of intra-operative samples, and 8/348 (2.3%) of TA samples. The pre-operative test had 100% PPV and 99% NPV, and the TA had 100% PPV and 98.6% NPV (Table 1). There was very good agreement (Figure) between pre- and intraoperative upper respiratory sampling, with a Kappa of 0.66, (95% CI 0.35–0.97). There was no statistical difference in results by sample type. Table 1. Comparison of intra-operative and pre-operative nasopharyngeal sample results, test characteristics and test concordance Table 2. Comparison of intra-operative nasopharyngeal and tracheal aspirate sample results, test characteristics and test concordance Figure 1 Percent agreement between pre-operative and intra-operative samples Conclusion There is a high PPV and NPV of pre-operative SARS-CoV-2 PCR testing among children undergoing anesthesia. These data can help inform guidelines regarding appropriate precautions for HCW performing high risk procedures in asymptomatic pediatric patients. Disclosures Suchitra Rao, MD, BioFire (Grant/Research Support) Samuel Dominguez, MD, PhD, BioFire (Consultant, Research Grant or Support)

Critical Evaluation of Impedance Phlebography for the Diagnosis of Deep Vein Thrombosis

1974 ◽  
Vol 31 (02) ◽  
pp. 273-278
Author(s):  
Kenneth K Wu ◽  
John C Hoak ◽  
Robert W Barnes ◽  
Stuart L Frankel
Keyword(s):  
Deep Vein Thrombosis ◽  
False Positive ◽  
False Negative ◽  
Critical Evaluation ◽  
Original Method ◽  
Vein Thrombosis ◽  
Negative Results ◽  
False Negative Results ◽  
Deep Vein ◽  
Positive Results

SummaryIn order to evaluate its daily variability and reliability, impedance phlebography was performed daily or on alternate days on 61 patients with deep vein thrombosis, of whom 47 also had 125I-fibrinogen uptake tests and 22 had radiographic venography. The results showed that impedance phlebography was highly variable and poorly reliable. False positive results were noted in 8 limbs (18%) and false negative results in 3 limbs (7%). Despite its being simple, rapid and noninvasive, its clinical usefulness is doubtful when performed according to the original method.

Scoring System for the Diagnosis of COVID-19

2020 ◽  
Vol 13 (1) ◽  
pp. 413-414 ◽  
Author(s):  
Mohamed Farouk Allam
Keyword(s):  
Scoring System ◽  
Clinical Symptoms ◽  
False Negative ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Pcr Assay ◽  
Negative Results ◽  
False Negative Results ◽  
Symptoms And Signs

Due to the international spread of COVID-19, the difficulty of collecting nasopharyngeal swab specimen from all suspected patients, the costs of RT-PCR and CT, and the false negative results of RT-PCR assay in 41% of COVID-19 patients, a scoring system is needed to classify the suspected patients in order to determine the need for follow-up, home isolation, quarantine or the conduction of further investigations. A scoring system is proposed as a diagnostic tool for suspected patients. It includes Epidemiological Evidence of Exposure, Clinical Symptoms and Signs, and Investigations (if available). This scoring system is simple, could be calculated in a few minutes, and incorporates the main possible data/findings of any patient.

Detection of Streptococcus pneumoniae in Sputum Samples by Real- Time PCR.

2020 ◽  
Vol 18 ◽  
Author(s):  
Pegah Shakib ◽  
Mohammad Reza Zolfaghari
Keyword(s):  
Streptococcus Pneumoniae ◽  
Real Time ◽  
Real Time Pcr ◽  
False Negative ◽  
Cross Sectional Study ◽  
Laboratory Culture ◽  
Cross Sectional ◽  
Negative Results ◽  
False Negative Results ◽  
Pcr Method

Background: Conventional laboratory culture-based methods for diagnosis of Streptococcus pneumoniae are time-consuming and yield false negative results. Molecular methods including real-time (RT)-PCR rapid methods and conventional PCR due to higher sensitivity and accuracy have been replaced instead traditional culture assay. The aim of the current study was to evaluate lytA gene for detection of Streptococcus pneumoniae in the cerebrospinal fluid of human patients with meningitis using real-time PCR assay. Material and Methods: In this cross-sectional study, a total of 30 clinical specimens were collected from patients in a period from September to December 2018. In order to evaluate the presence of lytA gene, conventional and real-time PCR methods were used without culture. Results: From 30 sputum samples five (16.66%) isolates were identified as S. pneumoniae by lytA PCR and sequencing. Discussion: In this research, an accurate and rapid real-time PCR method was used, which is based on lytA gene for diagnosis of bacteria so that it can be diagnosed. Based on the sequencing results, the sensitivity for detection of lytA gene was 100% (5/5).

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