scholarly journals When intuition falters: repeated testing accuracy during an epidemic

Author(s):  
James A. Hay ◽  
Joel Hellewell ◽  
Xueting Qiu

AbstractWidespread, repeated testing using rapid antigen tests to proactively detect asymptomatic SARS-CoV-2 infections has been a promising yet controversial topic during the COVID-19 pandemic. Concerns have been raised over whether currently authorized lateral flow tests are sufficiently sensitive and specific to detect enough infections to impact transmission whilst minimizing unnecessary isolation of false positives. These concerns have often been illustrated using simple, textbook calculations of positivity rates and positive predictive value assuming fixed values for sensitivity, specificity and prevalence. However, we argue that evaluating repeated testing strategies requires the consideration of three additional factors: new infections continue to arise depending on the incidence rate, isolating positive individuals reduces prevalence in the tested population, and each infected individual is tested multiple times during their infection course. We provide a simple mathematical model with an online interface to illustrate how these three factors impact test positivity rates and the number of isolating individuals over time. These results highlight the potential pitfalls of using inappropriate textbook-style calculations to evaluate statistics arising from repeated testing strategies during an epidemic.

2021 ◽  
Author(s):  
Trystan Leng ◽  
Edward M. Hill ◽  
Robin N. Thompson ◽  
Michael J. Tildesley ◽  
Matt J. Keeling ◽  
...  

AbstractBackgroundStrategies involving rapid testing have been suggested as a way of reopening schools that minimises absences while controlling transmission. We assess the likely impact of rapid testing strategies using lateral flow tests (LFTs) on infections and absences in secondary schools, compared to a policy of isolating year group bubbles upon a pupil returning a positive polymerase chain reaction (PCR) test.MethodsWe developed an individual-based model of a secondary school formed of exclusive year group bubbles (five year groups, with 200 pupils per year). By simulating infections over the course of a seven-week half-term, we compared the impact of differing strategies on transmission, absences, and testing volume. We also considered the sensitivity of results to underlying model assumptions.FindingsRepeated testing of year-group bubbles following case detection or regular mass-testing strategies result in a modest increase in infections compared to the policy of isolating year-group bubbles, but substantially reduce absences. When combined these two testing strategies can reduce infections to levels lower than would occur under year-group isolation, although such a policy requires a high volume of testing.InterpretationOur results highlight the conflict between the goals of minimising within-school transmission, minimising absences and minimising testing burden. While mass and targeted testing strategies can reduce school transmission and absences, it may lead to a large number of daily tests.


2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jonas Andersson ◽  
Azra Habibovic ◽  
Daban Rizgary

Abstract To explore driver behavior in highly automated vehicles (HAVs), independent researchers are mainly conducting short experiments. This limits the ability to explore drivers’ behavioral changes over time, which is crucial when research has the intention to reveal human behavior beyond the first-time use. The current paper shows the methodological importance of repeated testing in experience and behavior related studies of HAVs. The study combined quantitative and qualitative data to capture effects of repeated interaction between drivers and HAVs. Each driver ( n = 8 n=8 ) participated in the experiment on two different occasions (∼90 minutes) with one-week interval. On both occasions, the drivers traveled approximately 40 km on a rural road at AstaZero proving grounds in Sweden and encountered various traffic situations. The participants could use automated driving (SAE level 4) or choose to drive manually. Examples of data collected include gaze behavior, perceived safety, as well as interviews and questionnaires capturing general impressions, trust and acceptance. The analysis shows that habituation effects were attenuated over time. The drivers went from being exhilarated on the first occasion, to a more neutral behavior on the second occasion. Furthermore, there were smaller variations in drivers’ self-assessed perceived safety on the second occasion, and drivers were faster to engage in non-driving related activities and become relaxed (e. g., they spent more time glancing off road and could focus more on non-driving related activities such as reading). These findings suggest that exposing drivers to HAVs on two (or more) successive occasions may provide more informative and realistic insights into driver behavior and experience as compared to only one occasion. Repeating an experiment on several occasions is of course a balance between the cost and added value, and future research should investigate in more detail which studies need to be repeated on several occasions and to what extent.


Author(s):  
Andreas Osterman ◽  
Maximilian Iglhaut ◽  
Andreas Lehner ◽  
Patricia Späth ◽  
Marcel Stern ◽  
...  

AbstractA versatile portfolio of diagnostic tests is essential for the containment of the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) pandemic. Besides nucleic acid-based test systems and point-of-care (POCT) antigen (Ag) tests, quantitative, laboratory-based nucleocapsid Ag tests for SARS-CoV-2 have recently been launched. Here, we evaluated four commercial Ag tests on automated platforms and one POCT to detect SARS-CoV-2. We evaluated PCR-positive (n = 107) and PCR-negative (n = 303) respiratory swabs from asymptomatic and symptomatic patients at the end of the second pandemic wave in Germany (February–March 2021) as well as clinical isolates EU1 (B.1.117), variant of concern (VOC) Alpha (B.1.1.7) or Beta (B.1.351), which had been expanded in a biosafety level 3 laboratory. The specificities of automated SARS-CoV-2 Ag tests ranged between 97.0 and 99.7% (Lumipulse G SARS-CoV-2 Ag (Fujirebio): 97.03%, Elecsys SARS-CoV-2 Ag (Roche Diagnostics): 97.69%; LIAISON® SARS-CoV-2 Ag (Diasorin) and SARS-CoV-2 Ag ELISA (Euroimmun): 99.67%). In this study cohort of hospitalized patients, the clinical sensitivities of tests were low, ranging from 17.76 to 52.34%, and analytical sensitivities ranged from 420,000 to 25,000,000 Geq/ml. In comparison, the detection limit of the Roche Rapid Ag Test (RAT) was 9,300,000 Geq/ml, detecting 23.58% of respiratory samples. Receiver-operating-characteristics (ROCs) and Youden’s index analyses were performed to further characterize the assays’ overall performance and determine optimal assay cutoffs for sensitivity and specificity. VOCs carrying up to four amino acid mutations in nucleocapsid were detected by all five assays with characteristics comparable to non-VOCs. In summary, automated, quantitative SARS-CoV-2 Ag tests show variable performance and are not necessarily superior to a standard POCT. The efficacy of any alternative testing strategies to complement nucleic acid-based assays must be carefully evaluated by independent laboratories prior to widespread implementation.


2019 ◽  
Vol 6 (Supplement_2) ◽  
pp. S159-S159
Author(s):  
Michelle Rose ◽  
John Allen Myers ◽  
Nicholas Ryan ◽  
Alissa Prince ◽  
Morgan Talbot ◽  
...  

Abstract Background Previous research has shown millennials represent the fastest growing generation for those infected with the hepatitis C virus (HCV). Millennials are also a key driver in the opioid crisis, particularly in states of the Appalachian region including Kentucky. Despite research demonstrating a change in prevalence from baby boomers (born 1945–1965) to millennials (born 1980–1995), large representative studies providing evidence of the magnitude of this demographic shift are lacking in the United States. Our objective was to assess trends of HCV infection since 2016 in a large healthcare system located in an area of high prevalence of opioid use and HCV infection. Methods All individuals were screened for HCV infection in 2016, 2017, and 2018 within Norton Healthcare per standard risk-based criteria (e.g., injection drug users, baby boomers, etc.) as recommended by CDC, except for pregnant women who were universally screened since 2016. We tested for demographic shifts over time using longitudinal and time series analyses techniques Results A total of 86,243 individuals were screened for HCV infection from 2016 to 2018. Of those, 2,615 (3.0%) individuals screened positive for chronic HCV. The average age of those infected significantly decreased by an average of 3.7 years annually (from 47.3 years in 2016 to 39.9 years in 2018, P < 0.001). We forecast a plateau near the age of 28 years will be observed in just over 7 years. In addition, the proportion of millennials increased over time (33.6% in 2016, 42.4% in 2017 and 51.4% in 2018, P < 0.001), while baby boomers significantly decreased over time (44.0% in 2016, 38.8% in 2017, and 29.3% in 2018, P < 0.001). Lastly, over time, those with chronic HCV were more likely to be male (increasing from 49.6% to 54.4%, P = 0.008) and Hispanic (increasing from 1.6% to 17.7%, P < 0.001) Conclusion Our results suggest that HCV infection has become a predominately millennial disease, skipping a generation. These results correlate with trends seen with the opioid epidemic, which is driven by millennials. We conclude that the opioid crisis has led to a drastic demographic shift, and currently the typical HCV-infected individual is a younger male. Without interventions, this trend will continue for over seven years, plateauing near the demarcation of millennials and generation Z Disclosures All authors: No reported disclosures.


2021 ◽  
Author(s):  
kobi snitz ◽  
Danielle Honigstein ◽  
Reut Weisgross ◽  
Aharon Ravia ◽  
Eva Mishor ◽  
...  

Key to curtailing the COVID-19 pandemic are wide-scale testing strategies 1,2 . An ideal test is one that would not rely on transporting, distributing, and collecting physical specimens. Given the olfactory impairment associated with COVID-19 3-7 , we developed a novel measure of olfactory perception that relies on smelling household odorants and rating them online. We tested the performance of this real-time tool in 12,020 participants from 134 countries who provided 171,500 perceptual ratings of 60 different household odorants. We observed that olfactory ratings were indicative of COVID-19 status in a country, significantly correlating with national infection rates over time. More importantly, we observed remarkable indicative power at the individual level (90% sensitivity and 80% specificity). Critically, olfactory testing remained highly effective in participants with COVID-19 but without symptoms, and in participants with symptoms but without COVID-19. In this, the current odorant-based olfactory test stands apart from symptom-checkers (including olfactory symptom-checkers) 3 , and even from antigen tests 8 , to potentially provide a first line of screening that can help halt disease progression at the population level.


2021 ◽  
Vol 14 (1) ◽  
pp. 27-32
Author(s):  
Dedi Komarudin

The manufacture of tools such as machetes in Banten is still widely practiced, machetes are produced from a conventional forging process using a hammer by a blacksmith. Working as a blacksmith in the Banten area, especially in the village of the new village of lightning, was passed down from generation to generation as a traditional blacksmith, but over time the machetes produced by traditional blacksmiths began to be replaced by modern ones machete. The traditional golok of Kampung Baru Village, Petir, consists of two types, the regular machete and the sulangkar golok. The material commonly used by blacksmiths to make machetes is a vehicle spring sheet that is no longer used, while for making machetes, a blacksmith usually combines other materials during forging. The purpose of this study was to determine the differences in the mechanical and micro properties of the two types of golok, Banten cultural heritage. The research was carried out from the start of the search for the material, the manufacturing and forging processes and carried out testing. The results of the hardness test show that the value of the spring material is 423.1 HBW, SS 400 steel material 134.18 HBW, combination material or Sulangkar 735.15 HBW then the data results from the tensile test on steel material SS 400, Spring, Combination or Sulangkar are 442.52 MPa, 1334,60 MPa, 522.81 MPa. The results of the data from the impact test on Spring material, SS 400 steel, Combination or Sulangkar, namely 162 J, 34 J, 88 J. The results of automatic microscope testing and Scanning Electron Microscope (SEM) show the surface of the spring, SS 400 steel and combination materials.


2020 ◽  
Author(s):  
Marc Schneble ◽  
Giacomo De Nicola ◽  
Göran Kauermann ◽  
Ursula Berger

AbstractThe case detection ratio of COVID-19 infections varies over time due to changing testing capacities, modified testing strategies and also, apparently, due to the dynamics in the number of infected itself. In this paper we investigate these dynamics by jointly looking at the reported number of detected COVID-19 infections with non-fatal and fatal outcomes in different age groups in Germany. We propose a statistical approach that allows us to spotlight the case detection ratio and quantify its changes over time. With this we can adjust the case counts reported at different time points so that they become comparable. Moreover we can explore the temporal development of the real number of infections, shedding light on the dark number. The results show that the case detection ratio has increased and, depending on the age group, is four to six times higher at the beginning of the second wave compared to what it was at the peak of the first wave. The true number of infection in Germany in October was considerably lower as during the peak of the first wave, where only a small fraction of COVID-19 infections were detected. Our modelling approach also allows quantifying the effects of different testing strategies on the case detection ratio. The analysis of the dynamics in the case detection rate and in the true infection figures enables a clearer picture of the course of the COVID-19 pandemic.


2020 ◽  
Author(s):  
Omar Vesga ◽  
Andres F. Valencia ◽  
Alejandro Mira ◽  
Felipe Ossa ◽  
Esteban Ocampo ◽  
...  

AbstractMolecular tests for viral diagnostics are essential to confront the COVID-19 pandemic, but their production and distribution cannot satisfy the current high demand. Early identification of infected people and their contacts is the key to being able to isolate them and prevent the dissemination of the pathogen; unfortunately, most countries are unable to do this due to the lack of diagnostic tools. Dogs can identify, with a high rate of precision, unique odors of volatile organic compounds generated during an infection; as a result, dogs can diagnose infectious agents by smelling specimens and, sometimes, the body of an infected individual. We trained six dogs of three different breeds to detect SARS-CoV-2 in respiratory secretions of infected patients and evaluated their performance experimentally, comparing it against the gold standard (rRT-PCR). Here we show that viral detection takes one second per specimen. After scent-interrogating 9,200 samples, our six dogs achieved independently and as a group very high sensitivity, specificity, predictive values, accuracy, and likelihood ratio, with very narrow confidence intervals. The highest metric was the negative predictive value, indicating that with a disease prevalence of 7.6%, 99.9% of the specimens indicated as negative by the dogs did not carry the virus. These findings demonstrate that dogs could be useful to track viral infection in humans, allowing COVID-19 free people to return to work safely.


2020 ◽  
Author(s):  
Anne M Neilan ◽  
Elena Losina ◽  
Audrey C. Bangs ◽  
Clare Flanagan ◽  
Christopher Panella ◽  
...  

Background We projected the clinical and economic impact of alternative testing strategies on COVID-19 incidence and mortality in Massachusetts using a microsimulation model. Methods We compared five testing strategies: 1) PCR-severe-only: PCR testing only patients with severe/critical symptoms; 2) Self-screen: PCR-severe-only plus self-assessment of COVID-19-consistent symptoms with self-isolation if positive; 3) PCR-any-symptom: PCR for any COVID-19-consistent symptoms with self-isolation if positive; 4) PCR-all: PCR-any-symptom and one-time PCR for the entire population; and, 5) PCR-all-repeat: PCR-all with monthly re-testing. We examined effective reproduction numbers (Re, 0.9-2.0) at which policy conclusions would change. We used published data on disease progression and mortality, transmission, PCR sensitivity/specificity (70/100%) and costs. Model-projected outcomes included infections, deaths, tests performed, hospital-days, and costs over 180-days, as well as incremental cost-effectiveness ratios (ICERs, $/quality-adjusted life-year [QALY]). Results In all scenarios, PCR-all-repeat would lead to the best clinical outcomes and PCR-severe-only would lead to the worst; at Re 0.9, PCR-all-repeat vs. PCR-severe-only resulted in a 63% reduction in infections and a 44% reduction in deaths, but required >65-fold more tests/day with 4-fold higher costs. PCR-all-repeat had an ICER <$100,000/QALY only when Re≥1.8. At all Re values, PCR-any-symptom was cost-saving compared to other strategies. Conclusions Testing people with any COVID-19-consistent symptoms would be cost-saving compared to restricting testing to only those with symptoms severe enough to warrant hospital care. Expanding PCR testing to asymptomatic people would decrease infections, deaths, and hospitalizations. Universal screening would be cost-effective when paired with monthly retesting in settings where the COVID-19 pandemic is surging.


2020 ◽  
Author(s):  
Amirhoshang Hoseinpour Dehkordi ◽  
Reza Nemati ◽  
Pouya Tavousi

AbstractIt has been evident that the faster, more accurate, and more comprehensive testing can help policymakers assess the real impact of COVID-19 and help them with when and how strict the mitigation policies should be. Nevertheless, the exact number of infected ones could not be measured due to the lack of comprehensive testing. In this paper, first of all, we will investigate the relation of transmission of COVID-19 with age by observing timed data in multiple countries. Then, we compare the COVID-19 CFR with the age-demography data. and as a result, we have proposed a method for estimating a lower bound for the number of positive cases by using the reported data on the oldest age group and the regions’ population age-distributions. The proposed estimation method improved the expected similarity between the age-distribution of positive cases and regions’ populations. Thus, using the publicly accessible data for several developed countries, we show how the improvement of testing over the course of several months has made it clear for the community that different age groups are equally prone to becoming COVID positive. The result shows that the age demography of COVID-19 gets similar to the age-demography of the population, together with the reduction of CFR over time. In addition, countries with less CFR have more similar COVID-19’s age-distribution, which is caused by more comprehensive testing, than ones who have higher CFR. This leads us to a better estimation for positive cases in different testing strategies. Having knowledge of this fact helps policymakers enforce more effective policies for controlling the spread of the virus.


Sign in / Sign up

Export Citation Format

Share Document