Negative Home COVID Test No ‘Free Pass’ for Kids, Study Finds

Negative Home COVID Test No ‘Free Pass’ for Kids, Study Finds

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With the country looking increasingly to rapid testing as an off-ramp from the COVID-19 pandemic, a new study shows that the performance of the tests in children falls below standards set by regulatory agencies in the United States and elsewhere for diagnostic accuracy.

Experts said the findings, from a meta-analysis by researchers in the United Kingdom and Germany, underscore that, while a positive result on a rapid test is almost certainly an indicator of infection, negative results often are unreliable and can lead to a false sense of security.

“Real-life performance of current antigen tests for professional use in pediatric populations is below the minimum performance criteria set by WHO, the United States Food and Drug Administration, or the Medicines and Healthcare products Regulatory Agency (U.K.),” according to Naomi Fujita-Rohwerder, PhD, a research associate at the Cologne-based German Institute for Quality and Efficiency in Health Care (IQWiG), and her colleagues, whose study appears in BMJ Evidence-Based Medicine.

The researchers said that the study suggests that performance of rapid testing in a pediatric population is comparable to that in adults. However, they said they could not identify any studies investigating self-testing in children, which also could affect test performance.

Egon Ozer, MD, PhD, director of the center for pathogen genomics and microbial evolution at Northwestern University in Chicago, said the finding that specificity was high but sensitivity was middling “suggests that we should be very careful about interpreting negative antigen test results in children and recognize that there is a fair amount of uncertainty in the tests in this situation.”

Researchers from IQWiG, which examines the advantages and disadvantages of medical interventions, and the University of Manchester (England), conducted the systematic review and meta-analysis, which they described as the first of its kind to evaluate the diagnostic accuracy of rapid point-of-care tests for current SARS-CoV-2 infections in children.

They compiled information from 17 studies with a total 6,355 participants. They compared all antigen tests to reverse-transcription polymerase chain reaction (PCR). The studies compared eight antigen tests from six different brands. The rapid antigen tests, available from pharmacies and online stores, are widely used for self-testing in schools and testing toddlers before kindergarten.

The pooled diagnostic sensitivity of antigen tests was 64.2% and specificity was 99.1%.

Ozer noted that the analysis “was not able to address important outstanding questions such as the likelihood of transmitting infection with a false-negative antigen test versus a true-negative antigen test or how much repeated testing can increase the sensitivity.”

“In Europe, we don’t know how most tests perform in real life,” Fujita-Rohwerder said. “And even in countries like the United States, where market access is more stringent, we don’t know whether self-testing performed by children or sample collection in toddlers by laypersons has a significant impact on the diagnostic accuracy. Also, diagnostic accuracy estimates reported in our study may not apply to the current omicron or future variants of SARS-CoV-2 or vaccinated children. Hopefully, these essential gaps in the evidence will get addressed soon.”

Ozer said one takeaway from this study is negative antigen tests should not be considered a “free pass” in children, especially if the child is symptomatic, has been recently exposed to COVID-19, or is planning to spend time with individuals with conditions that place them at high risk for complications of COVID-19 infection. “In such cases, consider getting PCR testing or at least performing a repeat antigen test 36-48 hours after the first negative,” he said.

Fujita-Rohwerder said the low diagnostic sensitivity may affect the use of the tests. The gaps in evidence her group found in their study point to research needed to support evidence-based decision-making. “In particular, evidence is needed on real-life performance of tests in schools, self-testing performed by children, and kindergarten, [particularly] sample collection in toddlers by laypersons,” she said.

However, she stressed, testing is only a single measure. “Effectively reducing the spread of SARS-CoV-2 during the current pandemic requires multilayered mitigation measures,” she said. “Rapid testing represents one single layer. It can have its use at the population level, even though the sensitivity of antigen tests is lower than expected. However, antigen-based rapid testing is not a magic bullet: If your kid tests negative, do not disregard other mitigation measures.”

Edward Campbell, PhD, a virologist at Loyola University of Chicago, who serves on the board of LaGrange Elementary School District 102 outside Chicago, said the findings were unsurprising.

“This study generally looks consistent with what is known for adults. These rapid antigen tests are less sensitive than other tests,” said Campbell, who also runs a testing company for private schools in the Chicago area using reverse transcription-loop-mediated isothermal amplification technology. Even so, he said, “These tests are still effective at identifying people who are infectious to some degree. Never miss an opportunity to test.”

Fujita-Rohwerder disclosed no relevant financial conflicts of interest. Campbell owns Safeguard Surveillance.

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