scholarly journals Perform or perish: laboratory optimization to avoid false negative blood cultures in pneumococcal bacteremia

2019 ◽  
Vol 43 (4) ◽  
pp. 217-220 ◽  
Author(s):  
Vandana Kalwaje Eshwara ◽  
Tushar Shaw ◽  
Yasha Mukim ◽  
Gauri Kumar ◽  
Asha Kamath ◽  
...  
Keyword(s):  
Phase I ◽  
Phase Ii ◽  
False Negative ◽  
Blood Cultures ◽  
Negative Results ◽  
Pneumococcal Bacteremia ◽  
False Negative Results ◽  
Two Phases ◽  
Antigen Tests ◽  
Alternate Solution

Abstract We present the laboratory operations influencing the culture yield of pneumococci and suggest an alternate solution to the problem. Blood cultures of 136 adults and 19 pediatric patients were analyzed in two phases. In phase I, the laboratory operated only during weekdays but in phase II the laboratory provided 24-h services on all days. In phase I, successful bacterial isolation leading to testing of antimicrobial susceptibility was possible only in 51% of cases, while a significant 49% had failed to grow in subcultures due to autolysis resulting from delayed processing time. These false negative blood cultures were further confirmed as Streptococcus pneumoniae by commercial antigen tests. In phase II, we did not observe any false-negative results due to prompt subculturing protocols (p < 0.001). We also found that taking blood cultures on two occasions increases the yield by 46% among adults.

scholarly journals SARS-CoV-2 RNA detection using pooling of self-collected samples: Simple protocol may foster asymptomatic surveillance

2020 ◽  
Author(s):  
Giselle Ibette Lopez-Lopes ◽  
Rita de Cassia Compagnoli Carmona ◽  
Valéria Oliveira Silva ◽  
Cintia Mayumi Ahagon ◽  
Lincoln Spinazola do Prado ◽  
...  
Keyword(s):  
False Negative ◽  
Clinical Samples ◽  
Rna Detection ◽  
Negative Results ◽  
False Negative Results ◽  
Throat Wash ◽  
Asymptomatic Volunteers ◽  
Simple Protocol ◽  
Antigen Tests ◽  
Public Health Institute

1AbstractBackgroundSurveillance of COVID infection and isolation of infected individuals is one of the available tools to control the spread of SAR-CoV-2. Asymptomatic and pre symptomatic are responsible for substantial transmission. RNA or antigen tests are necessary to identify non-symptomatic individuals. We tested the feasibility of using samples pooling offering different collection alternatives (swab/throat wash/saliva) to volunteers of a public health institute.MethodsWe evaluated pool samples from frozen material from previously tested samples and a prospective collection from asymptomatic volunteers. Some collections were paired for comparison. Pools and some individual samples were extracted with QIAamp Viral RNA Mini Kit (Qiagen, USA) and/or Lucigen Quick Extract DNA extraction solution (BioSearch, USA) and submitted to rtPCR (Allplex, Seegene, Korea).ResultsA total of 240 samples from 130 new collections and 37 samples with known result were evaluated. Pool CT was generally higher than individual samples. Lucigen extraction showed higher CT, including false negative results for samples with high CT at Qiagen extraction. Paired Swab and TW samples showed comparable results. No volunteer from negative pools reported any symptom in the 2-3 days after collection.ConclusionsClinical samples pooling to detect SARS-CoV-2 RNA is feasible and an economical way to test for COVID-19, especially in surveillance strategies targeting more infectiousness, higher viremia individuals. The use of Lucigen reagents show lower sensibility that may lead to false negative results with lower viremia samples. Combining throat wash with saliva may provide and interesting self-collection alternative, but more comparative work is needed.

scholarly journals COVID-19 Testing – Impact of Prevalence, Sensitivity, and Specificity on Patient Risk and Cost

2020 ◽  
Author(s):  
Zoe C. Brooks ◽  
Saswati Das
Keyword(s):  
False Positive ◽  
False Negative ◽  
Test Methods ◽  
Antibody Testing ◽  
Patient Risk ◽  
Advantages And Disadvantages ◽  
Negative Results ◽  
False Negative Results ◽  
Antigen Tests ◽  
Positive Agreement

Since the beginning of the year 2020, the global healthcare system has been challenged by the threat of the SARS-COV 2 virus. Molecular, antigen, and antibody testing are the mainstay to identify infected patients and fight the virus. Molecular and antigen tests that detect the presence of the virus are relevant in the acute phase only. Serological assays detect antibodies to the Sars-CoV-2 virus in the recovering and recovered phase. Each testing methodology has its advantages and disadvantages. To evaluate the test methods, sensitivity (percent positive agreement - PPA) and specificity (percent negative agreement &ndash; PNA) are the most common metrics utilized, followed by the positive and negative predictive value (PPV and NPV), the probability that a positive or negative test result represents a true positive or negative patient. In this paper, we illustrate how patient risk and clinical costs are driven by false-positive and false-negative results. We demonstrate the value of reporting PFP (probability of false positive results), PFN (probability of false negative results), and costs to patients and healthcare. These risk metrics can be calculated from the risk drivers of PPA and PNA combined with estimates of prevalence, cost, and Reff number (people infected by one positive SARS COV-2).

scholarly journals COVID-19 Testing

2020 ◽  
Vol 154 (5) ◽  
pp. 575-584 ◽  
Author(s):  
Zoe C Brooks ◽  
Saswati Das
Keyword(s):  
False Positive ◽  
False Negative ◽  
Test Methods ◽  
Antibody Testing ◽  
Advantages And Disadvantages ◽  
Negative Results ◽  
False Negative Results ◽  
Antigen Tests ◽  
The Individual ◽  
Positive Agreement

Abstract Objectives To illustrate how patient risk and clinical costs are driven by false-positive and false-negative results. Methods Molecular, antigen, and antibody testing are the mainstay to identify infected patients and fight the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To evaluate the test methods, sensitivity (percent positive agreement [PPA]) and specificity (percent negative agreement [PNA]) are the most common metrics utilized, followed by the positive and negative predictive value—the probability that a positive or negative test result represents a true positive or negative patient. The number, probability, and cost of false results are driven by combinations of prevalence, PPA, and PNA of the individual test selected by the laboratory. Results Molecular and antigen tests that detect the presence of the virus are relevant in the acute phase only. Serologic assays detect antibodies to SARS-CoV-2 in the recovering and recovered phase. Each testing methodology has its advantages and disadvantages. Conclusions We demonstrate the value of reporting probability of false-positive results, probability of false-negative results, and costs to patients and health care. These risk metrics can be calculated from the risk drivers of PPA and PNA combined with estimates of prevalence, cost, and Reff number (people infected by 1 positive SARS-CoV-2 carrier).

scholarly journals COVID-19 Testing – Impact of Prevalence, Sensitivity, and Specificity on Patient Risk and Cost

2020 ◽  
Author(s):  
Zoe C. Brooks ◽  
Saswati Das
Keyword(s):  
False Negative ◽  
Test Methods ◽  
Antibody Testing ◽  
Patient Risk ◽  
Advantages And Disadvantages ◽  
Negative Results ◽  
False Negative Results ◽  
Antigen Tests ◽  
Positive Agreement ◽  
Test Result

Since the beginning of the year 2020, the global healthcare system has been challenged by the threat of the SARS-COV 2 virus. Molecular, antigen, and antibody testing are the mainstay to identify infected patients and fight the virus. Molecular and antigen tests that detect the presence of the virus are relevant in the acute phase only. Serological assays detect antibodies to the Sars-CoV-2 virus in the recovering and recovered phase. Each testing methodology has its advantages and disadvantages. To evaluate the test methods, sensitivity (percent positive agreement - PPA) and specificity (percent negative agreement &ndash; PNA) are the most common metrics utilized, followed by the positive and negative predictive value (PPV and PNV), the probability that a positive or negative test result represents a true positive or negative patient. In this paper, we illustrate how patient risk and clinical costs are driven by false-positive and false-negative results. We demonstrate the value of reporting PFP (probability of false positives), PFN (probability of false negatives), and costs to patients and healthcare. These risk metrics can be calculated from the risk drivers of PPA and PNA combined with estimates of prevalence, cost, and Reff number (people infected by one positive SARS COV-2).

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).

COVID-19: how nuclear medicine can provide a differential diagnosis in very dubious case

Coronaviruses ◽  
2020 ◽  
Vol 01 ◽  
Author(s):  
Maria Silvia De Feo ◽  
Viviana Frantellizzi ◽  
Giuseppe De Vincentis
Keyword(s):  
Infectious Disease ◽  
Differential Diagnosis ◽  
Ct Scan ◽  
Imaging Technique ◽  
False Negative ◽  
Clinical Signs ◽  
Negative Results ◽  
Infectious Disease Department ◽  
False Negative Results ◽  
99Mtc Hmpao

Background: We present the case of a 55-year-old woman, admitted to the Infectious Disease Department of Policlinico Umberto I, Rome, in mid-March 2020, with suspicion of COVID-19 infection. Objective: The rRT-PCR was negative and the following CT scan, performed to exclude false-negative results and help diagnosis, was inconclusive. Methods: It was decided to submit the patient to 99mTc-HMPAO-labelled leukocyte scan. Results: This exam led to the diagnosis of infective endocarditis. Conclusion: In the present pandemic scenario, 99mTc-HMPAO-labelled leukocyte scan represents a reliable imaging technique for differential diagnosis with COVID-19 in patients with confusing clinical signs, possible false-negative rRT-PCR results and inconclusive CT scan.

Sign in / Sign up

Export Citation Format

Share Document