How often-discarded blood samples could track Canadians’ health

At the height of the pandemic, Canadians became familiar with the concept of waste-water testing to track SARS-CoV-2 through human waste flushed down the toilet.

But there is another bodily fluid that often goes to waste, and the head of Canada’s COVID-19 Immunity Task Force says it should be drawn upon more often to inform public health.

“Waste blood,” is how CITF executive director Tim Evans describes the vials of blood left over after patients undergo routine tests. Rather than ditch those specimens – the usual practice – Dr. Evans and a working group he leads are advocating for testing them in a systematic way that could help detect everything from the ill effects of environmental toxins to the true prevalence of some chronic diseases – and perhaps even the next frightening new pathogen.

A permanent waste-blood surveillance network could be “one of the really exciting silver linings of the pandemic,” said Dr. Evans, who also directs the School of Population and Global Health in the Faculty of Medicine at McGill University. But bringing the concept to life will require money and the ability to overcome fragmented provincial health systems that often undermine national co-operation.

Waste blood is already being used in several Canadian research projects arising from the pandemic, including one that is testing blood gathered in the emergency departments of 16 pediatric hospitals to estimate the share of children who have recently had COVID-19. As well, Canadian Blood Services and the CITF have been testing donated blood from nine provinces for antibodies to the virus since the spring of 2020. They plan to keep it up until March, when federal funding for the effort is set to expire.

As the COVID-19 Immunity Task Force winds down, Dr. Evans is leading a working group on waste blood that includes representatives from academia, provincial public health labs, the Public Health Agency of Canada, Canadian Blood Services and Héma-Québec, that province’s blood agency.

Their intention is to have a proposal, including a request for federal funding, ready by the end of the year for a permanent waste-blood testing network that would go beyond one-off research projects forged in the fire of a public-health emergency. They’ve tentatively dubbed it HemaNet.

“We think if you can keep something like this going in peacetime, rather than ramping it up in the context of an emergency, it will be massively more efficient,” Dr. Evans said.

Deborah Money, a professor in the department of Obstetrics and Gynecology at the University of British Columbia and an expert in reproductive infectious diseases, saw first-hand the challenges of starting a waste-blood testing program when she led a study using tubes of blood left over from prenatal tests during the pandemic.

Getting ethics approvals, privacy assessments and data-sharing agreements with every provincial and hospital lab she hoped to include proved “cumbersome and difficult,” even though Dr. Money and her research partners were not looking for information that could identify patients. She just wanted labs to test prenatal blood samples for antibodies to SARS-CoV-2 and share the de-identified results for population-level snapshots of how widely the virus had spread.

“For the most part,” Dr. Money said, “the individuals involved have a perspective that release of data is dangerous. And some of us have a perspective that not using the data for the sake of the population is dangerous.”

Antibodies to SARS-CoV-2, the virus that causes COVID-19, can be detected in blood for months after infection. That makes widespread testing of waste blood a more reliable measure of infection rates than lab-based PCR or at-home antigen tests, which catch active infections. But seroprevalence testing, as it is called, is backward-looking, which means speed is of the essence, particularly during a public-health emergency.

Dr. Money and her team managed to complete their study, but the bumpy road to data-sharing agreements delayed publication until April, when the pandemic had waned. The researchers gave up on including as many samples as they would have liked from Ontario, where agreements with dozens of hospital labs would have been necessary.

Caroline Quach-Thanh, a pediatric infectious disease doctor and medical microbiologist at Sainte-Justine children’s hospital in Montreal, foresees a smoother process for testing pediatric waste blood now that an umbrella group called POPCORN (Pediatric Outcome Improvement through Coordination of Research Networks) has been created with funding from the Canadian Institutes of Health Research.

POPCORN established a process to collect leftover blood from children who have samples drawn at pediatric emergency rooms. The specimens, 4,800 of which have come in so far, will be tested for COVID-19 antibodies, giving public-health officials a picture of immunity to inform childhood vaccination recommendations. Researchers are awaiting the first batch of results.

Dr. Quach-Thanh, POPCORN’s director, said by e-mail that pediatric waste blood could also be tested for emerging pathogens and to provide a snapshot of childhood immunity to measles.

General waste-blood testing could also be a source of knowledge about less common pathogens, such as those carried by insects making their way north as the climate changes.

Along with its widespread SARS-CoV-2 immunity testing program, Canadian Blood Services already does some limited testing of leftover samples to keep an eye out for pathogens such as Babesia microti, which is carried by deer ticks, and food-borne illnesses such as hepatitis E. It tests for West Nile virus during mosquito season and Chagas disease in at-risk donors, on top of regular tests for blood-borne pathogens such as HIV and hepatitis C.

Steve Drews, the associate director of microbiology at Canadian Blood Services, sees plenty of potential in expanding the role of blood operators in public-health surveillance, especially if their liquid resources are supplemented with the testing of waste water and other sources of waste blood. Blood donors are fairly representative of the healthy population, but they don’t include groups such as long-term care residents and children, who are too young to donate.

“Putting the data together from different sources helps you get a more comprehensive picture of what’s going on,” he said.