The summer of 2024 saw a wave of COVID-19 infections spreading globally, causing increases in reported cases and hospital admissions, with wastewater surveillance indicating higher true exposure levels. Social media reports of COVID-19–like symptoms with negative test results prompted investigation into test reliability.
The U.S. Food and Drug Administration (FDA) told The BMJ that most existing tests used to detect COVID-19 infections appeared effective with circulating variants. Maria Sundaram, an associate research scientist at the Marshfield Clinic Research Institute, noted that while there was limited data proving antigenic tests could detect current variants, this might have been moot, as the vast majority of circulating variants, including FLiRT variants, descended from omicron variants that tests identified effectively.
The tests' reliability stemmed from targeting the nucleocapsid protein instead of the spike protein. Popular at-home antigenic tests, including BinaxNow, Flowflex, and Clinitest, used antibodies targeting this more preserved viral component.
The Atlanta Center for Microsystems Engineered Point of Care Technologies, serving as the national test verification center, collected global variant samples for laboratory testing. Early unpublished data indicated manufacturers had improved antibody sensitivity in newer test generations, including multiplex assays screening for COVID-19 and influenza infections simultaneously.
A 2022 Cochrane review of 155 studies found:
- Tests detected 73% of symptomatic cases
- Presymptomatic detection rate was 55%
- Tests showed highest sensitivity in the first week of symptoms
- Performance varied with upper respiratory tract viral load.
Wilbur Lam, Professor at Emory and Georgia Institute of Technology, recommended sequential testing at 24-hour intervals to achieve polymerase chain reaction (PCR)-comparable sensitivity. Negative results could occur from:
- Testing timing in infection cycle
- Poor storage conditions
- Expired tests
- Incorrect test administration
- Symptoms caused by other diseases.
The FDA maintained a MedWatch reporting system for test-related issues, including significant concerns about counterfeits during the pandemic, and emphasized following manufacturer-specific instructions.
Scientists stressed the continued importance of testing for tracking viral dynamics and community spread. While current strains presented influenza-like symptoms, infections carried long COVID risk, which vaccination reduced but did not eliminate. Scientists noted baseline testing data remained essential for assessing strain severity.
The authors declared having no competing interests.
