Tag: covid testing

Categories : COVID Lab Tests and ImagingTags :

Rapid Blood Assay to Test for COVID Immunity

On By ModernMedia
Blood sample being drawn
Photo by Hush Naidoo Jade Photography on Unsplash

Researchers have developed a rapid blood assay that measures the strength and duration of an individual’s immunity to SARS-CoV-2. This test will allow population-scale monitoring immunity and vaccine effectiveness. This will help to design revaccination strategies for vulnerable immunosuppressed individuals, according to a study published by the researchers from Mount Sinai in Nature Biotechnology.

The test, which measures the activation of T cells, is performed in under 24 hours and can be scaled up significantly.

“The assay we have created has the ability to measure the population’s cellular immunity and broadly test the efficacy of novel vaccines,” said one of the study’s senior authors, Ernesto Guccione, PhD, Professor at Mount Sinai. “We know that vulnerable populations don’t always mount an antibody response, so measuring T cell activation is critical to assess the full extent of a person’s immunity. Additionally, the emergence of SARS-CoV-2 variants like Omicron, which evade most of the neutralising ability of antibodies, points to the need for assays that can measure T cells, which are more effective against emerging variants of concern.”

Long-term protection from viral infection is mediated by both antibodies and T cell response. Many recent studies point to the importance of determining T cell function in individuals who have recovered from or been vaccinated against COVID to help design vaccination campaigns. However, before this study, measurement of T cell responses has been rarely performed because of the associated technical challenges.

Researchers optimised qPCR-based assays that had the potential to be globally scalable, sensitive, and accurate tests. They then selected the two assays that offered the most scalability. One, the qTACT assay, was accurate and sensitive but had a relatively longer processing time of 24 hours per 200 blood samples, a moderate price, and a medium level of technical skill. The other, the dqTACT assay, was accurate and had a reduced processing time and cost, and required minimal lab experience, making it easy to implement.

The dqTACT assay has recently received the European CE-IVD (in vitro diagnostics) certification, while U.S. Food and Drug Administration and European Medicines Agency clinical validation is ongoing.

“The assays presented here are based on the ability of SARS-CoV-2 T cells to respond to peptides covering different proteins of the virus,” said another senior author, Jordi Ochando, PhD, Assistant Professor at Mount Sinai. “With the possibility of using different peptide pools, our approach represents a flexible strategy that can be easily implemented to detect the presence of T cells responding to different viral proteins. These T cells have an important role in protection from emerging mutant strains, thus immediately gauging the impact that viral mutations might have on cellular immunity.”

Megan Schwarz, a graduate student at Icahn Mount Sinai and first author of the study, added: “Precise measurement of cellular responses underlying virus protection represents a crucial parameter of our levels of immune defence.”

Source: EurekAlert!

Categories : COVIDTags :

Is it Possible to Detect COVID in Exhaled Breaths?

On By ModernMedia
Source: CDC

In a study published in Influenza and Other Respiratory Viruses, researchers were able to detect SARS-CoV-2 viral RNA in droplets from the exhaled breaths and coughs of COVID patients.

COVID is assumed to be transmitted mainly by respiratory droplets. However, probable aerosol transmission has been reported to occur under certain conditions. The researchers sought to address the lack of information on viral load in exhaled breath samples,as well as the size and concentration of exhaled endogenously generated droplets in relation to viral load. Additionally, the relationship between the viral load in upper airway diagnostic samples and aerosol samples needed to diagnose.
For the study, researchers analysed exhalations by two different methods during 20 normal breaths, 10 airway opening breaths (which involves deep inhalation followed by relaxed exhalation), and 3 coughs.

PCR detection of SARS-CoV-2 RNA in aerosols was possible in 10 out of 25 participants. Viral RNA presence in aerosol was mainly detected in cough samples (8 samples), but also in normal breaths (4 samples) and in airway opening breaths (3 samples).  

“Our data confirm findings from other researchers that SARS-CoV-2 can be detected in aerosol particles < 5µm and highlight the small amount of exhaled aerosol needed for detection. Of specific interest were findings from the airway opening maneuver, which is thought to generate particles mainly from the small airways,” said lead author Emilia Viklund, PhD student at the University of Gothenburg, in Sweden. “COVID causes a lot of damage in this region, and it would be of great interest to further explore the amount of exhaled virus and the course of disease, as well as the infectious potential of exhaled virus.”

Source: Wiley

Categories : COVIDTags :

Are Saliva Swabs the Best Way to Test for Omicron?

On By ModernMedia
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With the Omicron variant now dominating, a local study showed that, if confirmed, testing for COVID could be more accurate with much easier saliva sampling.

University of Cape Town researchers reported in a paper uploaded to medRxiv [PDF] that in Omicron cases, saliva samples yielded more accurate results in PCR analyses compared to nasal swabs.

With the Delta variant, on the other hand, nasal swabs were more accurate, according to the group, led by Diana Hardie, MBChB, MMedPath, who also heads the diagnostic virology laboratory at Groote Schuur Hospital.

The findings came from an analysis of 382 patients tested at Groote Schuur from August through this month, with viral whole-genome sequencing performed on isolates from those with positive results.

All patients had both saliva and mid-turbinate nasal samples taken for RT-PCR analysis. The ‘gold standard’ for positivity in the study was detection of SARS-CoV-2 RNA with either swab.

For the Delta variant, the positive percent agreement for each sampling method, in comparison with this ‘gold standard’, was 71% for saliva and 100% for the nasal swabs. But Omicron reversed the trend, with 100% agreement between saliva samples and the gold standard, but only 86% for nasal swabs.

COVID testing has used nasal swabs as standard since the discovery of the virus, but that may no longer be appropriate in an Omicron-dominated pandemic landscape, the authors concluded.

“These findings suggest that the pattern of viral shedding during the course of infection is altered for Omicron with higher viral shedding in saliva relative to nasal samples resulting in improved diagnostic performance of saliva swabs,” Hardie and colleagues wrote.

They noted, as have others, that Omicron is distinguished by “more than 50 distinct mutations.” While these increased infectivity, they could also have other effects, including the tissues it may prefer to infect.

The researchers cited a recent unpublished lab study from Hong Kong indicating that Omicron preferentially infects the upper airway. Not only does it suggest Omicron is less lethal, but also that the many mutations confer “altered tissue tropism.”

However, saliva sampling is not as simple as it sounds. At Groote Schuur, patients were instructed to swab the inside of the mouth for a total of at least 30 seconds. They were also told not to eat, drink, smoke, or chew anything for at least 30 minutes beforehand.

While most of the COVID testing kits in the US and elsewhere rely on nasal swabs, any change to saliva sampling would take months – by which time Omicron may have been displaced by another variant.

Source: MedPage Today

Categories : COVID PaediatricsTags :

Kids’ Spit Could be a Great COVID Test

On By ModernMedia
Photo by CDC

Saliva samples are easy to obtain and useful for measuring antibodies to SARS-CoV-2 in children, which could improve epidemiological surveillance in school settings. The study followed over 1500 children who went to summer schools in Barcelona last year. The results were published in BMC Medicine.

One of the pressing questions during this pandemic has been to understand children’s susceptibility to SARS-CoV-2 infection and how they infect others. An obstacle to answer this question is that most infections in children are mild or asymptomatic, and are therefore missed. To establish whether an individual has been exposed to SARS-CoV-2 in the past, virus-specific antibodies in blood need to be detected. Measuring antibody prevalence over time in a cohort of children can provide very valuable epidemiological information. However, this requires techniques that are both sensitive and minimally invasive.

In this study, performed through the Kids Corona platform, the team led by Carlota Dobaño, from the Barcelona Institute for Global Health (ISGlobal), and Iolanda Jordan, from Hospital Sant Joan de Déu (HSJD), used saliva instead of blood to measure virus-specific antibodies in over 1500 children who attended different summer schools in Barcelona in 2020, as well as around 400 adult staff. Two saliva samples per participant were analysed, one at the beginning and one at the end of the camp stay, and different antibody types (IgG, IgA and IgM) targeting different viral antigens were measured.

The study found that 3.2% of the participants developed antibodies between the first and second sample, indicating new infections. This is six times higher than the infection rate estimated by weekly PCR screening. “It has been reported that some children can be positive for antibodies despite being negative by PCR, which suggests that they can generate an immune response that prevents the establishment of SARS-CoV-2 infection,” explained Dobaño, first author of the study. It could also be because asymptomatic children have lower viral loads or that their viral clearance is faster.

Furthermore, the analysis shows that the percentage of new infections was higher in adults (2.94%) than in children (1.3%), suggesting differences in infection and transmission dynamics. Finally, contrary to blood tests, asymptomatic people had higher levels of anti-Spike antibodies in saliva, suggesting these antibodies play a protective role in respiratory mucosae. “This means that anti-Spike antibodies in saliva could be used to measure protective immunity upon vaccination, especially in the case of intranasal vaccines,” said senior study co-author Gemma Moncunill.

“We previously demonstrated in other Kids Corona studies that saliva is useful for detecting virus by PCR. With this study, we demonstrate that it’s also an effective and much friendlier way to measure antibodies, making it the ideal sample for children, instead of the more invasive nasal swab,” said Jordan.

Source: EurekAlert!

Categories : COVIDTags :

COVID Test Sensitivity Changes with Circadian Rhythm

On By ModernMedia
Source: Fusion Medical Animation on Unsplash

A new study suggests that the sensitivity of tests for SARS-CoV-2 vary throughout the day according to the body’s circadian rhythm, which could have implications for how the disease is managed.

Carl Johnson, Cornelius Vanderbilt Professor of Biological Sciences, wondered how the virus might act differently depending on the time of day and the body’s circadian rhythms, and collaborated with colleagues to determine if the percentage of people testing positive for COVID varies based on time of day. They found that people were up to two times as likely to have an accurate positive test result if they tested in the middle of the day compared to at night. Their findings were published in the Journal of Biological Rhythms.

The data support the hypothesis that COVID acts differently in the body based on our natural circadian rhythm, which has also been implied by studies of other viral and bacterial infections. COVID virus shedding, when infected cells release infectious virus particles into the blood and mucus, appears to be more active around midday due to modulation of the immune system by our biological clock.

“Taking a COVID test at the optimal time of day improves test sensitivity and will help us to be accurate in diagnosing people who may be infected but asymptomatic,” Prof Johnson said. Their results indicate that viral load is lower after 8 pm. If people choose to get tested at that time, there could be a higher chance of a false-negative result. False negatives can be harmful to the community and for the patient, who might not seek additional care due to their negative test result.

A difference in COVID viral shedding throughout the day would help inform treatment for the disease. As Johnson and his co-authors report, the peak shedding in the afternoon, when patients are more likely to interact with others or seek medical care, could play a role in increasing the spread of the virus in hospitals and the wider community.

Further research is needed to confirm the diurnal nature of SARS-CoV-2. Experimentally testing COVID patients to see if individuals shed the virus differently throughout the day would have important public health implications, Prof Johnson said.

Source: Vanderbilt University

Categories : COVIDTags :

Lateral Flow Tests now Approved for Travellers to England

On By ModernMedia
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Fully vaccinated passengers arriving in England and most under 18s arriving from non red-list countries (which now includes South Africa) can use a lateral flow test (LFT) on or before day 2 of their arrival in England, the UK government has announced.

LFTs must be taken as soon as possible on the day of arrival in England or at the latest before the end of a passenger’s second day and can now be purchased from the list of private providers on GOV.UK from as little as £22 – significantly cheaper than PCR tests.

LFTs for international travel must be purchased from a private provider as NHS Test and Trace lateral flow tests cannot be used for international travel. Passengers who have already bought a PCR to use for travel do not need to buy another test as PCRs can still be used.

Passengers have to take a photo of their lateral flow test and booking reference supplied by the private provider, then send it back to them to verify the result. Failure to do so could result in a fine of £1000 (R20 000). It is also possible for passengers to book a test at some airport testing centres. People using PCR tests for travel will have their test reported by the company they purchase the test from.

Anyone who tests positive will need to isolate and take a confirmatory PCR test, at no additional cost to the traveller, which can be genomically sequenced to help identify new variants. PCR tests can be accessed free of charge by ordering in the usual way through NHS Test and Trace – via nhs.uk/coronavirus or by calling 119.  Test providers will be expected to advise people to self-isolate and direct people towards the NHS Test and Trace booking page.

In addition, all travellers must complete a passenger locator form beforehand, including providing a test booking reference number supplied by a testing provider.

However, these new rules apply only to those arriving in England: anyone travelling on to Ireland, Northern Ireland, Scotland, Wales, the Channel Islands or the Isle of Man within 10 days after arrival in England have to follow the rules for testing and quarantine in those places.

Those passengers who are not fully vaccinated with an authorised vaccine returning from a non-red list destination must still take a pre-departure test (antigen/PCR), a PCR test on day 2 and day 8 test and complete 10 days’ self-isolation (with the option of doing Test to Release on day 5).

Source: UK Government

Categories : COVIDTags :

SARS-CoV-2 Can be Detected in Aircraft Wastewater

On By ModernMedia
Photo by Lukas Souza on Unsplash

Australian researchers have found SARS-CoV-2 virus in wastewater samples from long haul flights arriving from outside the country, demonstrating that they can detect it even before passengers show symptoms.

The CSIRO and University of Queensland scientists worked with Qantas to show that wastewater surveillance can provide valuable data for public health agencies.

CSIRO lead author Dr Warish Ahmed said as global travel returns, testing wastewater of incoming flights could screen incoming passengers for COVID at points of entry.

“It provides an extra layer of data, if there is a possible lag in viral detection in deep nasal and throat samples and if passengers are yet to show symptoms,” Dr Ahmed said.

“The rapid on-site surveillance of wastewater at points of entry may be effective for detecting and monitoring other infectious agents that are circulating globally and provide alert to future pandemics.”

Co-author Professor Jochen Mueller from UQ’s Queensland Alliance for Environmental Health Sciences said wastewater testing could be a useful extra tool.

“The paper recommends that wastewater surveillance be used as part of an efficient clinical surveillance and quarantine system – providing multiple lines of evidence of the COVID infection status of passengers during international travel,” Professor Mueller said.

The study, published in Environment International, analysed wastewater samples from 37 Australian Government repatriation flights from COVID hotspots including India, France, UK, South Africa, Canada and Germany between December 2020 and March 2021.

The research found SARS-CoV-2 in wastewater samples from 24 of the 37 repatriation flights (65%) despite all passengers (except children under age five) having tested negative to the virus 48 hours before boarding. Virus is shed in the faeces of infected people about two to five days before showing symptoms.

Traces of SARS-CoV-2 can also be detected in wastewater from previously infected people who still shed the coronavirus, but are no longer infectious – although typically a weaker signal.

During 14 days of the passengers’ mandatory quarantine upon arrival in Australia, clinical tests identified only 112 COVID cases among the 6570 passengers (1.7%).

Monitoring of wastewater has a number of applications. Through its wastewater monitoring programme, the Durban University of Technology found that the recent unrest in South Africa was a superspreader event that drove up cases in KwaZulu-Natal.

Source: University of Queensland

Categories : COVID General InterestTags :

Kids Cunningly Spoof COVID Tests to Skip School

On By ModernMedia
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School children in the UK have found an ingenious way to get out of school — by deliberately compromising COVID tests using soft drinks or fruit juice to produce false positives.

Children returned to in-person learning in March in the UK, with regular COVID testing to monitor for infection and infected students being sent home. 

However, after three months of regular testing, a school in Merseyside had reports of students who had found that either drinking fruit-flavored juice or misusing them as an analyte had the potential to provide a false-positive result.  

The trick involves “spoofing” a lateral flow device (LFD) which is designed to detect COVID antibodies.

LFDs come in the form of cartridges containing a nitrocellulose membrane strip and absorbent paper with dried test reagents affixed, which include antibodies labelled with gold particles for visibility. When these reagents are mixed with the analyte from a test sample, they migrate through the nitrocellulose strip and over the test (T) line where the SARS-CoV-2 monoclonal antibody is located.

A key part of the trick is not mixing the sample fluid with the buffer, BBC’s Mark Lorch found.

The liquid buffer solution maintains an ideal pH for the antibodies, and is key to the correct function of the test. The critical role of the buffer is highlighted by if cola is mixed with the buffer, then the LFDs behave correctly, returning a negative result for COVID.

Without the buffer, the antibodies in the test are fully exposed to the acidic pH of the beverages. And this has a dramatic effect on their structure and function. Proteins such as antibodies fold up into very specific structures, and even a small change to the chains can dramatically impact a protein’s function. Changing the pH could cause the antibodies used in the test to no longer function correctly and incorrectly binding. By diluting the drink

In a study made available on the medRxiv preprint server, researchers tested the ability of various types of soft drinks to produce false positive results. They found that the presence of sugar and acidity was necessary to produce the false positives. The researchers also recommended 

Source: BBC News

Categories : COVIDTags : 1 Comment

Case Positivity Rate in SA Breaches The Crucial 10% Mark

On By ModernMedia

Although new COVID cases have not yet shown an upward surge, the fact that the test positivity rate had climbed past 10% is cause for concern.

According to health minister Dr Zweli Mkhize, the 2383 new infections recorded in the past 24 hours came from 23 352 tests at a positivity rate of 10.2%. Yesterday the positivity rate stood at 9.86%, and in the days beforehand had been gradually creeping upward.

The government has previously expressed concern when the positivity rate (the percentage of COVID tests that return positive) reaches the 10% and 12% marks. In late November, ahead of the second wave, the case positivity rate was 14.5%. Some provinces of South Africa are reporting rates well in excess of this, particularly the Northern Cape which last week had a reported positivity rate of 24.1%.

Dr Mkhize also reported that there were 72 Covid-19 related deaths in the past 24 hours. The health minister also reported that across SA there were now 171 860 people who had received their first shot of the two-dose Pfizer vaccine.

With these latest figures, there are now 1 637 848 cumulative cases and 55 874 cumulative fatalities since the outbreak of the coronavirus in SA in March last year. However, the true toll may be much higher, as South Africa’s ‘excess deaths’, those which are above the average rate of deaths from all causes, were up to 2.67 times higher than the official toll. A report from a team at the SA Medical Research Council and University of Cape Town believed that around 85% of those excess deaths were due to COVID.

Source: Times Live

Categories : COVID Lab Tests and ImagingTags :

Siemens COVID Antigen Test Kit Receives German Approval

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Siemens Healthineers announced on Wednesday that their antigen self-test kit, which uses samples from a nasal swab, has received limited special approval from the Federal Office for Drugs and Medical Devices (BfArM) for self-use by laypeople in Germany. The regular conformity assessment procedure for the standardised ‘CE‘ mark was also initiated for personal use by laypeople.

“With the provision of the COVID-19 antigen rapid test for possible use by laypeople in Germany, we are breaking new ground and are thus continuing to fulfill our social responsibility to support a return to normal social life,” said Bernd Ohnesorge, Head of Europe, Middle East, and Africa Regions, Siemens Healthineers

The practicability of the kit was confirmed by a study in which 50 participants without medical training personally carried out the test by following the instructions for use. The test already has a CE mark for use by specialist groups for taking samples in the nose.

“The CLINITEST COVID-19 Antigen Self-Test offers users a high degree of flexibility in performing the test with very good quality results,” said Christoph Pedain, Head of Point of Care Diagnostics at Siemens Healthineers.

Siemens’ COVID-19 Antigen Self-Test takes 15 minutes to give a result, using samples taken from both nostrils using a swab. The swab is then washed out in a reagent, which detaches a specific protein from the surface of the virus. The resulting liquid is dripped into a recess in the test cassette.

The test liquid migrates into the field of view of the cassette within 15 minutes, becoming visible as a line. The position and number of lines indicate as to whether there is a positive or negative test result, or whether there was a problem, necessitating a repeat of the test.

In the instructions, the tester is shown the steps to achieve a test result, including instructions on how to proceed according to the test result. A negative test result does not exempt the user from any local COVID regulations. Currently, the test kit is also available in the UK.

Source: Siemens