Early on in this year's coronavirus pandemic, SARS-CoV-2, experts began to explore whether the pool testing approach used in blood banking could be adapted to increase testing capacity in coronavirus diagnostics and protect those with a high mortality risk from the coronavirus. This would protect those at greater risk from asymptomatic individuals, including the medical and care staff that look after them.

Viral infections are challenging because people can be contagious before developing symptoms. Studies have said individuals can spread the coronavirus two days before the onset of clinical symptoms and viral load is at its highest almost a day before any symptoms become apparent. 

It would take a year to test everyone individually and pool testing would solve much of the problem. Pool testing is just what it sounds like. Samples from several individuals are pooled and tested together in a single tube and only if the pool result is positive do the samples need to be tested individually. It is a well-established and safe procedure in blood banking and would help to meet the high demand for testing in the mass coronavirus screening programs needed in the early identification and isolation of asymptomatic individuals.

A group at Saarland University Hospital in Homburg began doing sample pooling in mid-March to successfully protect vulnerable patients from infection by asymptomatic SARS-CoV-2 carriers and they are now screening residents and staff at nursing and residential care homes in Saarland. Their RT-PCR molecular biological test method allows them to test 30 people at once.

Sigrun Smola is Professor of Virology at the Saarland University and Director of the Institute of Virology at Saarland University Hospital. Credit: Rüdiger Koop, UKS

In countries like the U.S., getting approval for new tests required getting past an onerous regulatory burden and there was simply not enough testing capacity in the diagnostic labs. The U.S. CDC did not help by being a bottleneck for tests and then sending faulty reagents, which spurred government into granting emergency use authorizations for private companies that know what they are doing. It wouldn't have been a problem if the same pool sampling available for blood tests were simply made possible under guidelines labs must follow. In a regulatory system where CDC and FDA let HRI Labs lie about being government approved and claim they can detect weedkillers in breast milk without consequences, preventing quality labs from helping during a pandemic makes little sense.

Detectable even in a pool of 30 people

In the Saarland tests, even one positive out of 30 in a single test tube was detected. When a positive result occurred, a second phase of testing on the individual samples identified the infected person or persons. 

As some individuals do not develop further symptoms, but remain contagious for some time, it is crucial that these asymptomatic and presymptomatic patients are identified. This allows for detection of infection 'hot spots' and to isolate infected individuals effectively rather than hoping massive lockdowns, with numerous bizarre groups like marijuana shops exempted, will work.

In the proof of concept, the pool testing procedure developed in Homburg is being used to screen residents and staff at 131 nursing and residential care homes in Saarland. Around 22,000 people will be screened. Such a number is challenging for academics but the private sector can do it easily, if governments get out of their own way.