Pooling samples could accelerate new coronavirus testing
Virologists from Germany have displayed that combining samples and only testing individual samples when there is a positive result for the group could massively improve the convenience of coronavirus testing.
Testing is a major limiting factor in the response to the COVID-19 pandemic.
Healthcare systems across the world have been struggling to cope with the demand for testing, with many countries having insufficient capacity even to test healthcare workers. Laboratory infrastructure is stretched and, occasionally, completely overwhelmed by the pandemic.
Scientists from Germany, which includes had an admirable testing capacity, have published information on a testing strategy that they state could massively increase capacity in laboratories all over the world.
The strategy involves pooling samples from multiple persons and only testing individual samples if the effect from the group test is positive. This may potentially save a large number of unnecessary tests.
The details now come in The Lancet Infectious Diseases.
How come testing so important?
Testing is an essential area of the response to the pandemic. Germany’s high testing rates have been linked to the country’s lower death toll. Around 7,569 persons have died of COVID-19 in Germany, weighed against 31,930 in the United Kingdom and 30,560 in Italy. That is despite Germany having a larger population than both these countries.
Knowing who gets the virus is critical in protecting against them from coming into connection with others, particularly among persons who are most at risk, such as for example older adults and those with serious illnesses.
This is not just a case of isolating persons with symptoms, however, as people can carry the virus without experiencing any observeable symptoms at all. People can even be contagious prior to the onset of symptoms - actually, viral load reaches its highest around a day before any symptoms appear - making diagnostic tests essential.
“Prevention is merely possible if we use large-scale testing to recognize asymptomatic persons and therefore avert infection of the most vulnerable,” explains senior study author Prof. Sigrun Smola, director of the Institute of Virology at Saarland University Medical Center in Germany.
How does testing work?
To check for a SARS-CoV-2 infection, scientists take swabs from the nose or back of the throat to check for genetic material from the virus. This might sound simple, nonetheless it involves several frustrating steps in the laboratory, that may take several hours.
To speed things up, the scientists behind the new study took inspiration from blood banks, which frequently use a method called sample pooling.
The approach works by combining several samples before performing the experimental workup, and only testing individual samples if the group sample has a positive result. This can prevent many unnecessary individual tests.
The scientists say that the technique is simple to perform and may expand the capability of laboratories when “large numbers of asymptomatic people ought to be screened.”
Focus on the approach began in March, when the researchers started pooling samples from medical staff without symptoms of COVID-19. They tested a variety of pool sizes, starting from four samples to 30 samples per pool.
The test was so sensitive that the team could incorporate samples from 30 different people in a single test tube.
“Even if only one individual in that group of 30 was infected, we still obtained a positive result for the pooled test. If a pool had a positive result, we then conducted a second phase of testing on the average person samples to identify the infected person or persons.”
- Prof. Sigrun Smola
After testing 1,191 samples in this manner, only 267 tests were essential to identify the 23 persons who had coronavirus. In a standard testing format, laboratories would have to test all of the samples individually. This process, therefore, saved over 900 tests.
“If the rate of infection is low and if a lot of the pools are negative, this may save significant amounts of test kits and increase the test capacity of the existing infrastructure” adds Prof. Smola.
Care home trials
Because of the success of these experiments, various nursing and residential care homes - which house a few of the persons at highest risk - are actually enrolling in the program. In fact, during writing, 131 homes in Saarland have signed up for the screening program, that will test both residents and staff. That comes to around 22,000 persons in total.
Prof. Smola says that the team can be getting requests for help from elsewhere.
“We've also received numerous urgent inquiries from hospitals in Germany and abroad, as testing capacity limitations are proving to become a critical issue currently.”
As your final note, it is crucial to caution that although this technique provides “sufficient diagnostic accuracy,” the scientists do say that it could not discover “borderline positive” samples in large pools.
A person may have a “borderline positive” result if indeed they contracted the infection two or three 3 weeks before undergoing the ensure that you are now recovering.
In order to avoid missing diagnoses such as these, the scientists recommend choosing an appropriate pool size for different infection scenarios and pooling fewer samples if there can be borderline cases in the cohort.
Source: www.medicalnewstoday.com
