scholarly journals Covid-19: PCR testing is suspended at private laboratory after high rate of false negatives

BMJ ◽  
2021 ◽  
pp. n2535
Author(s):  
Ingrid Torjesen
Keyword(s):  
High Rate ◽  
False Negatives ◽  
Private Laboratory

scholarly journals Research on Property and Model Optimization of Multiclass SVM for NIDS

2013 ◽  
Vol 347-350 ◽  
pp. 3696-3701 ◽  
Author(s):  
Jian Hao Song ◽  
Gang Zhao ◽  
Jun Yi Song
Keyword(s):  
Intrusion Detection ◽  
Intrusion Detection System ◽  
Detection System ◽  
High Rate ◽  
Support Vector ◽  
False Negatives ◽  
Online Data ◽  
Detection Systems ◽  
Network Intrusion ◽  
Multiclass Svm

By investigating insufficiency of typical artificial intelligence algorithms aiming at the high rate of False-Positives and False-Negatives in the Intrusion Detection Systems (IDS), this paper presents an approach that Support Vector Machine (SVM) is embedded in Network Intrusion Detection System (NIDS). At the same time, by using online data and K-fold cross-validation method, this paper proposes a method to optimize the attributes and model of SVM respectively. Experimental results show that by using this method as the detection core of the intrusion detection system, the rate of False-Negatives in IDS can be reduced significantly.

scholarly journals A simple correction for non-independent tests

2018 ◽  
Author(s):  
Jaime Derringer
Keyword(s):  
Statistical Significance ◽  
Multiple Comparisons ◽  
Psychological Research ◽  
False Positives ◽  
High Rate ◽  
Effective Number ◽  
False Negatives

Psychologists wrestle with how to best handle multiple comparisons, while maintaining a balance between false positives and false negatives. Undercorrection, such as ignoring the presence of multiple comparisons altogether, is known to yield an unacceptably high rate of false positives. Overcorrection, such as treating all tests as independent when they are not, results in overly conservative evaluations of statistical significance. This tutorial demonstrates $M_{eff}$ correction, a method for adjusting statistical significance thresholds for multiple comparisons, without the assumption of independence of tests. This method, in which the effective number of tests ($M_{eff}$) is estimated from the correlations among the variables being tested, was developed and validated in the field of genetics, but is based on statistical concepts (eigenvalues) that are very familiar to psychologists. $M_{eff}$ correction can be applied in psychological research to balance the necessity of correction for multiple comparisons with the concerns that arise from complex, correlated tests.

scholarly journals Digital PCR for high sensitivity viral detection in false-negative SARS-CoV-2 patients

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Paolo Poggio ◽  
Paola Songia ◽  
Chiara Vavassori ◽  
Veronica Ricci ◽  
Cristina Banfi ◽  
...  
Keyword(s):  
Present Report ◽  
Quantitative Polymerase Chain Reaction ◽  
Diagnostic Testing ◽  
False Negative ◽  
High Sensitivity ◽  
Digital Pcr ◽  
High Rate ◽  
Viral Gene ◽  
False Negatives ◽  
Gene Copies

AbstractPatients requiring diagnostic testing for coronavirus disease 2019 (COVID-19) are routinely assessed by reverse-transcription quantitative polymerase chain reaction (RT-qPCR) amplification of Sars-CoV-2 virus RNA extracted from oro/nasopharyngeal swabs. Despite the good specificity of the assays certified for SARS-CoV-2 molecular detection, and a theoretical sensitivity of few viral gene copies per reaction, a relatively high rate of false negatives continues to be reported. This is an important challenge in the management of patients on hospital admission and for correct monitoring of the infectivity after the acute phase. In the present report, we show that the use of digital PCR, a high sensitivity method to detect low amplicon numbers, allowed us to correctly detecting infection in swab material in a significant number of false negatives. We show that the implementation of digital PCR methods in the diagnostic assessment of COVID-19 could resolve, at least in part, this timely issue.

Structure of Palladium Single-Crystal Films Prepared by Flash Evaporation onto (001) NaCl Substrates

1970 ◽  
Vol 28 ◽  
pp. 456-457
Author(s):  
L. E. Murr ◽  
G. Wong
Keyword(s):  
Single Crystal ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
High Rate ◽  
Flash Evaporation ◽  
Optimum Load ◽  
Single Crystal Films ◽  
Crystal Films ◽  
A Current

Palladium single-crystal films have been prepared by Matthews in ultra-high vacuum by evaporation onto (001) NaCl substrates cleaved in-situ, and maintained at ∼ 350° C. Murr has also produced large-grained and single-crystal Pd films by high-rate evaporation onto (001) NaCl air-cleaved substrates at 350°C. In the present work, very large (∼ 3cm2), continuous single-crystal films of Pd have been prepared by flash evaporation onto air-cleaved (001) NaCl substrates at temperatures at or below 250°C. Evaporation rates estimated to be ≧ 2000 Å/sec, were obtained by effectively short-circuiting 1 mil tungsten evaporation boats in a self-regulating system which maintained an optimum load current of approximately 90 amperes; corresponding to a current density through the boat of ∼ 4 × 104 amperes/cm2.

Rapid Freezing of Freeze-Etch Specimens

1980 ◽  
Vol 38 ◽  
pp. 752-755
Author(s):  
A. Elgsaeter ◽  
T. Espevik ◽  
G. Kopstad
Keyword(s):  
Low Temperature ◽  
Metal Surface ◽  
Relative Velocity ◽  
Thermal Contact ◽  
High Rate ◽  
Rapid Freezing ◽  
Temperature Decrease ◽  
Freeze Etching

The importance of a high rate of temperature decrease (“rapid freezing”) when freezing specimens for freeze-etching has long been recognized1. The two basic methods for achieving rapid freezing are: 1) dropping the specimen onto a metal surface at low temperature, 2) bringing the specimen instantaneously into thermal contact with a liquid at low temperature and subsequently maintaining a high relative velocity between the liquid and the specimen. Over the last couple of years the first method has received strong renewed interest, particularily as the result of a series of important studies by Heuser and coworkers 2,3. In this paper we will compare these two freezing methods theoretically and experimentally.

Exploring the Validity and Operational Impact of Using Allied Health Assistants to Conduct Dysphagia Screening for Low-Risk Patients Within the Acute Hospital Setting

2020 ◽  
Vol 29 (4) ◽  
pp. 1944-1955 ◽  
Author(s):  
Maria Schwarz ◽  
Elizabeth C. Ward ◽  
Petrea Cornwell ◽  
Anne Coccetti ◽  
Pamela D'Netto ◽  
...  
Keyword(s):  
At Risk ◽  
Allied Health ◽  
Assessment Tool ◽  
Hospital Setting ◽  
Low Risk ◽  
False Negatives ◽  
Exact Agreement ◽  
Risk Patients ◽  
Impact Phase ◽  
Operational Impact

Purpose The purpose of this study was to examine (a) the agreement between allied health assistants (AHAs) and speech-language pathologists (SLPs) when completing dysphagia screening for low-risk referrals and at-risk patients under a delegation model and (b) the operational impact of this delegation model. Method All AHAs worked in the adult acute inpatient settings across three hospitals and completed training and competency evaluation prior to conducting independent screening. Screening (pass/fail) was based on results from pre-screening exclusionary questions in combination with a water swallow test and the Eating Assessment Tool. To examine the agreement of AHAs' decision making with SLPs, AHAs ( n = 7) and SLPs ( n = 8) conducted an independent, simultaneous dysphagia screening on 51 adult inpatients classified as low-risk/at-risk referrals. To examine operational impact, AHAs independently completed screening on 48 low-risk/at-risk patients, with subsequent clinical swallow evaluation conducted by an SLP with patients who failed screening. Results Exact agreement between AHAs and SLPs on overall pass/fail screening criteria for the first 51 patients was 100%. Exact agreement for the two tools was 100% for the Eating Assessment Tool and 96% for the water swallow test. In the operational impact phase ( n = 48), 58% of patients failed AHA screening, with only 10% false positives on subjective SLP assessment and nil identified false negatives. Conclusion AHAs demonstrated the ability to reliably conduct dysphagia screening on a cohort of low-risk patients, with a low rate of false negatives. Data support high level of agreement and positive operational impact of using trained AHAs to perform dysphagia screening in low-risk patients.

Clinically Meaningful Change

Methodology ◽  
2019 ◽  
Vol 15 (3) ◽  
pp. 97-105
Author(s):  
Rodrigo Ferrer ◽  
Antonio Pardo
Keyword(s):  
Effect Size ◽  
False Negative ◽  
False Negative Rate ◽  
Point Of View ◽  
Skewed Distribution ◽  
Effect Sizes ◽  
False Negatives ◽  
Large Size ◽  
Before And After ◽  
Post Test

Abstract. In a recent paper, Ferrer and Pardo (2014) tested several distribution-based methods designed to assess when test scores obtained before and after an intervention reflect a statistically reliable change. However, we still do not know how these methods perform from the point of view of false negatives. For this purpose, we have simulated change scenarios (different effect sizes in a pre-post-test design) with distributions of different shapes and with different sample sizes. For each simulated scenario, we generated 1,000 samples. In each sample, we recorded the false-negative rate of the five distribution-based methods with the best performance from the point of view of the false positives. Our results have revealed unacceptable rates of false negatives even with effects of very large size, starting from 31.8% in an optimistic scenario (effect size of 2.0 and a normal distribution) to 99.9% in the worst scenario (effect size of 0.2 and a highly skewed distribution). Therefore, our results suggest that the widely used distribution-based methods must be applied with caution in a clinical context, because they need huge effect sizes to detect a true change. However, we made some considerations regarding the effect size and the cut-off points commonly used which allow us to be more precise in our estimates.

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