In medicine, children are often “assumed to be miniature versions of adults,” said Jennifer Dien Bard, director of the clinical microbiology and virology laboratory at Children’s Hospital Los Angeles. “But they’re not just little adults. It is really important that with any test available, that there are specific strategies for children and their specific needs.
In the rush to clear treatments, vaccines, and diagnostics for widespread use, companies often neglect to include children in early trials that test whether products or therapies are safe and effective. But tests for viruses, bacteria and other infectious microbes that give stellar results for adults don’t always translate perfectly for children.
The reasons for these differences are not always obvious, Dr Pollock said. For example, children’s immune systems might be better able to spot and sequester certain infectious invaders, making them more difficult to detect with standard tests.
In a study, published in the Journal of Clinical Microbiology in October, Dr. Pollock and her team gathered data from nine pediatric hospitals across the country, all of which reported relatively low numbers of viruses in children without symptoms. Another, which has yet to be published in a peer-reviewed scientific journal, alludes to a similar trend in sick children.
Confused by the terms relating to coronavirus testing? Let us help you:
- Antibody: A protein produced by the immune system that can recognize and attach specifically to specific types of viruses, bacteria, or other invaders.
- Antibody test / serological test: A test that detects specific antibodies to the coronavirus. Antibodies start to appear in the blood about a week after the coronavirus has infected the body. Because antibodies take so long to develop, an antibody test cannot reliably diagnose an ongoing infection. But it can identify people who have been exposed to the coronavirus in the past.
- Antigen test: This test detects pieces of coronavirus protein called antigens. Antigenic tests are quick, only take five minutes, but are less accurate than tests that detect the genetic material of the virus.
- Coronavirus: Any virus belonging to the Orthocoronavirinae family of viruses. The coronavirus that causes Covid-19 is known as SARS-CoV-2.
- Covid19: The disease caused by the new coronavirus. The name is the abbreviation for coronavirus disease 2019.
- Isolation and quarantine: Isolation is the separation of people who know they have a contagious disease from those who do not. Quarantine refers to restricting the movement of people who have been exposed to a virus.
- Nasopharyngeal swab: A long flexible stick with a soft swab that is inserted deep into the nose to take samples from the space where the nasal cavity meets the throat. Samples for coronavirus tests can also be collected with swabs that do not penetrate as deep into the nose – sometimes called nasal swabs – or oral or throat swabs.
- Polymerase chain reaction (PCR): Scientists use PCR to make millions of copies of genetic material in a sample. Tests using PCR allow researchers to detect the coronavirus even when it is rare.
- Viral load: The amount of virus in a person’s body. In people infected with the coronavirus, the viral load may peak before starting to show symptoms, if symptoms do appear.
Laboratory tests, such as those that use a technique called polymerase chain reaction, or PCR, are sensitive enough to uncover these low-level infections, Dr Pollock said. But the virus may not be present in high enough amounts to be discovered by a rapid test, such as those that detect only relatively large amounts of coronavirus antigens or protein fragments. The Binax NOW is one of those tests.
Many of these children “are going to be negative on rapid tests,” said Dr Pollock. “This has an impact on our way of thinking about schools and daycares.”
Some children may be naturally predisposed to harboring fewer viruses. It was also possible that the children in those studies were all taken too late in their infections, when the virus was already gone. If this were the case, Dr Pollock said, these children may have already carried or even transmitted the virus in large quantities, but they were not tested during this time. It would be difficult to disentangle these scenarios without testing many more children, she said.