COVID-19 rapid antigen tests are common tools for quickly checking for the virus. Many people store these tests at home, leading to a frequent question: can they be used effectively after their printed expiration date? Understanding the science behind these dates is important for informed testing decisions.
Understanding Test Expiration Dates
COVID-19 rapid antigen tests contain chemical reagents and antibodies designed to detect viral proteins. These biological materials have a limited shelf life and can degrade over time.
Test strip antibodies bind to viral antigens, indicating a positive result. Over time, these antibodies deteriorate, reducing their ability to accurately detect the virus. Liquid solutions in some kits can also evaporate, affecting test function.
Manufacturers determine initial expiration dates through rigorous accelerated stability studies. These studies expose test components to elevated temperatures, simulating aging to establish how long the test performs reliably under recommended storage.
The U.S. Food and Drug Administration (FDA) authorizes tests and their shelf lives. Initial expiration dates were often conservative due to limited data. As manufacturers gather more data, they can submit it to the FDA to request extended expiration dates.
This means a test kit’s printed expiration date might have passed, but its actual, FDA-authorized shelf life could be longer.
The Risks of Using an Expired Test
Using a COVID-19 test past its true expiration date carries a risk of inaccurate results. The primary concern is an increased likelihood of a false negative. A false negative occurs when the test indicates a person does not have COVID-19, but they are actually infected.
This inaccuracy happens because degraded test components, like antibodies, may no longer effectively capture viral proteins. A degraded test might fail to produce a positive result even if viral material is present. This can lead to a false sense of security and unknowingly spread the virus.
While false negatives are more likely, false positives with expired tests are generally less common. Degraded components are more prone to not reacting than reacting incorrectly. However, any inaccurate result has broader implications.
For individuals, a false negative can delay medical care or prevent necessary isolation, prolonging illness and increasing transmission risk. For public health, unreliable tests distort infection rates and hinder outbreak control.
What to Do When Your Test is Expired
If your COVID-19 rapid antigen test has passed its printed expiration date, first verify its actual shelf life. Many tests have extended FDA expiration dates. Check the FDA’s website for a comprehensive list of authorized at-home tests and updated expiration dates, often including lot numbers to confirm your specific kit’s validity.
If your test is truly expired, do not use it. Expired, unused rapid COVID-19 tests are not regulated medical waste and can be disposed of in regular household trash. Place them in a sealed bag before disposal to limit access.
To obtain new, valid tests, check pharmacies and retailers. Some health insurance plans may cover costs. Government programs and community health clinics may also offer free tests.
If immediate testing is needed and a valid rapid antigen test is unavailable, consider alternative options. PCR tests are highly accurate and more sensitive than rapid antigen tests, especially for early or asymptomatic infections. These tests are usually performed by healthcare providers or at designated sites.