LEESBURG, Va. — As the National Institute for Automotive Service Excellence (ASE) concludes its 50th anniversary year, the association is is offering service professionals the opportunity to take an official ASE practice questions at no charge.
To receive a free practice questions voucher, individuals should login or create a myASE account at my.ase.com. From the store tab, they should click on ASE practice questions Vouchers and then practice questions Voucher. Check the box for practice questions voucher, enter the code ASE50th and click apply to get the free voucher.
An email containing the voucher code will be sent to the email address in the participants myASE account. The deadline to request a free practice questions voucher is Jan. 31.
Once an automotive service professional receives their practice questions voucher, it can be redeemed at asepractice.com and can be used for the A1-A8, C1, G1, L1, P2, T2, T4, T6 or T8 practice tests.
Individuals have 60 days from the date they redeem a voucher code for a practice questions to complete their review test. It is possible to stop at any point and return later to complete the test by entering the same code.
American Liver Foundation: “Liver Function Tests.”
KidsHealth: “Blood Test: (Liver) Hepatic Function Panel.”
Mayo Clinic: “Cirrhosis,” “Hepatitis B,” “Liver Function Tests.”
Royal Society of Chemistry: “Enzymes.”
World Health Organization: “What Is Hepatitis?”
Lab Tests Online: “Liver Panel,” “Tips on Blood Testing.”
University of Rochester Medical Center: “D-Dimer.”
American College of Gastroenterology: "ACG Practice Guideline: Evaluation of Abnormal Liver Chemistries."
Cleveland Clinic: “Tests to Diagnose Gallstone Disease.”
An everyday activity for an embedded software developer is designing an interface for the software component they are working on. An interface describes the interactions that can be performed with the component, its behaviors, and its inputs and outputs. Unfortunately, many poorly thought-through interfaces out in the wild make it more difficult for developers to use them effectively. This post will explore five tips for designing software interfaces that all embedded software developers should follow.
When designing an interface, try to follow industry-standard terminology and techniques to make your interface memorable. Even though most IDEs today have some intelligence for code completion, I find that it doesn’t always work. Being forced to look up the interface can interrupt development when a developer is “in the flow.”
For example, if you are designing a digital input/output interface, you might consider defining your interface function and method names like:
While I’ve always liked having an init function, having a deinit always felt awkward. I think a better interface that more closely follows object-oriented paradigms would be:
We would want to avoid names for interfacing with hardware that are unclear.
I have found that any interface I design seems to become unwieldy if it grows beyond 10–12 functions. The human mind can only store 7–12 pieces of information in short-term “RAM.” If more than that is required, it becomes more difficult to remember. Limiting the size of an interface to 10-12 is usually more than enough for what a component needs to do.
If the interface grows beyond 10–12 functions, it’s a sign that the component is trying to do too much! Developers, at that point, should carefully explore whether the component should be broken up into multiple components with a more well-defined purpose. Doing this can Boost the code structure, portability, and reusability of the component. Developers will also, more likely than not, be able to remember the interface better!
Test-Driven Development is an excellent tool for developers who want to write testable code and avoid “debug later” coding practices. However, TDD does have a further use in that we can use it to create tests that verify how the interface behaves as expected.
Early in the interface design process, developers will often create a list of functions or methods they want to include. Then, they’ll take an initial guess at what the inputs and outputs of those functions will be. Once the initial list is created, developers should make a list of tests for their component that will be used to prove that their component works.
With their initial test list in hand, developers can start to build out unit tests that require the developer to build the interface. As they work through each test, they’ll discover that their initial interface design will evolve to meet the system’s needs. When the tests are completed, two things will occur. First, a list of tests will describe how to interact with the component and the interface. Second, a component will be production ready.
While designing an interface, developers should follow SOLID principles. SOLID includes the open-closed principle, which states, “Software entities should be open for extension but closed for modification.” The idea here is that once we define our interface, we don’t want to modify it, but we want to be able to extend it if we need to add new functionality.
When interacting with hardware using C, such as with a digital input/output peripheral, we can build an interface that allows us to add features to the driver by extension. For example, I might include the following two functions in my interface:
These two functions would provide low-level access to the hardware peripheral registers. Developers could build any number of custom modules and interfaces based on the application at hand that extends the simple digital input/output interface provided by the driver. In this case, careful planning allows us to easily extend the interface without modifying our low-level driver.
Nearly 80% of embedded software developers use C to develop their embedded systems. At first glance, this can make it difficult for developers to reuse their interfaces without first creating interface templates that are copied and pasted. Using C seems not to offer abstractions as we have in C++. In C++, we can create a class with virtual methods to define our abstract interface. We want to abstract our interfaces when we need to change the underlying code. For example, if I want my digital input/output driver to work for two different microcontrollers.
In C, we can use a little trick to get similar behavior in our interfaces. The trick is to not define our interface as a list of prototype functions in a header but to define our interface as a list of function pointers in a structure like the below:
bool (*Init)( const DioConfig_t * const Config);
bool (*Read)(const DioObj_t * const, DioData_t * const DioData);
bool (*Write)(const DioObj_t * const, DioData_t * const DioData);
When we define our structure variable, we can assign the function that will be called as follows:
const Dio_t Dio =
I can easily change what low-level driver I am accessing by changing the structure initialization. For example, for an STM32 microcontroller, I might use the following:
const Dio_t Dio =
For an MSP430, I might use something like:
const Dio_t Dio =
The application code, at this point, doesn’t care what the underlying Dio function call is! If I want to initialize Dio, I simply call:
What’s cool about that is that it looks a lot like I’m making a call to a method in a class, but I’m using C! I also have a nice abstraction that decouples my application code from the underlying hardware calls. That’s a win-win!
Developers create new interfaces all the time when they implement new modules. The trick is to do so that the interfaces are natural, memorable, and easily extendable. There is often a temptation to create the interface and move on; However, the interface is perhaps the essential element of a component. Once the interface is set, making changes can lead to massive headaches and efforts to change them.
This post explored a few essential tips to help you design your embedded software interfaces. Following these minimal best practices will help you design memorable and extendable interfaces and keep developers from being tripped up during development.
Google announced a long overdue full design overhaul for its Google Home app in October 2022. It comes with a Material You look, better controls for smart home appliances, and improved camera feed functionalities. The company promised to offer a preview program for this new Home release and gather early feedback from users to iron out any issues. This preview program is now finally live, and you can sign up for a chance to get in on it from your Google Home app’s settings.
To join the program, make sure you’ve updated your Google Home app to the latest available version and head to the settings menu. The option to join the preview program is available under the app’s Settings in the Public Preview section.
Note that even if you’re on the latest version, it might still take some time for this settings pane to become available to you. Even when you’ve successfully signed up, it might still take a few days or weeks until the new experience becomes available to you.
Google makes clear that the preview program is just that. It’s possible that the app doesn’t properly work for you or that you run into bugs and issues that haven’t been reported yet. In any case, it’s simple to switch back to the previous version when you need to, simply hitting a button in the app’s settings under Public Preview. It’s not possible to turn off or on individual features, though.
In the meantime, learn all about what you can expect in the new version of the Google Home app. You can look forward to a new media player, custom spaces for different activities and groups, and a better app design for Wear OS.
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Few illnesses instill as much fear as Alzheimer's, a fatal neurodegenerative disease that destroys memory and identity. The dread is compounded by the uncertainty that often surrounds the diagnosis of the most common form of dementia.
Brain autopsies remain the only way to know for sure whether someone had the disease, which the Centers for Disease Control and Prevention estimates affects 6.5 million people in the United States. Over the past several years, sophisticated tests such as spinal taps and specialized PET scans have become available - but they are invasive and costly and not routinely used.
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As a result, Alzheimer's is frequently misdiagnosed, especially in the early stages. Other illnesses, including depression, can have similar symptoms and require other treatments.
But simple blood tests designed to help doctors diagnose Alzheimer's now are on the market. More are on the way. The tests are seen as an important scientific advance, but have ignited debate about how and when they should be used.
Some experts say much more research is needed before the new tests can be widely deployed, especially in primary-care settings. Others say there already is sufficient information on the accuracy of some tests. All agree that no single test is perfect and physicians still should perform a complete clinical assessment.
Widespread use of the tests may be some time off in the future - after insurance coverage improves and even more accurate next-generation tests become available. For now, none is covered by Medicare, and private insurance coverage is patchy.
- - -
How do Alzheimer's blood tests work?
In the past few years, scientific and technological advances have made it possible to detect in the blood tiny fragments of brain proteins implicated in Alzheimer's.
That has prompted experts in academia and industry to develop blood tests for the disease. Some of the tests detect a sticky protein called amyloid beta, while others look for another protein called tau. Some search for both or other markers of disease. The abnormal accretions of amyloid plaques and tau tangles are the defining characteristics of Alzheimer's.
So far, the tests have been used mostly in clinical trials, but a few are being sold on the commercial market. They are designed to complement doctors' assessments based on symptoms and other tests, not replace them.
If you have concerns about memory or reasoning issues, you should talk to your family and doctor. Just because the tests are available does not mean people should try to get them, experts say.
- - -
Which tests are available? How much do they cost?
At least three tests - by C2N Diagnostics, Quest Diagnostics and Quanterix - are available in most states outside clinical trials.
Quest, which charges $500, said some health plans are paying for its test. C2N charges $1,250 and offers financial assistance for eligible patients. Quanterix declined to provide a price but said its test is much cheaper than amyloid PET scans, which can cost $5,000 or more. All the companies are working to secure broader insurance coverage.
Eli Lilly and Roche also have developed tests but for now are using them only in trials.
- - -
Who should get the tests?
There is a wide range of opinions on this.
Some experts say it is too early to use the tests in regular clinical care. Others say they can be used in memory centers with confirmatory tests such as PET scans or spinal taps. Some say the tests are a useful tool that can be used broadly once they are covered by insurance.
Still, many scientists agree on an important point: That the tests, which must be ordered by doctors, should be reserved for people with cognitive problems - persistent memory or logic issues, not just the occasional forgetfulness we all experience because of normal aging or stress.
Many researchers say it is too early to use the tests for people who do not have symptoms, because there isn't adequate research involving that group and the issue is rife with scientific uncertainty and ethical questions.
"The test results are intended to be used in adults presenting with cognitive impairment who are being evaluated for [Alzheimer's disease] and must be interpreted in conjunction with other diagnostic tools," Quanterix said in a statement in July when it launched its test.
C2N uses a similar description, and company officials stress that their test is not designed for the "worried well" group of people.
Quest says its test is for people with or without symptoms. Quest relies on physicians "to use their own discretion when ordering tests," said spokeswoman Kimberly Gorode, adding that the test's "clinical utility will increase once there is an FDA-approved treatment for Alzheimer's disease."
- - -
Why would I want to know if I have Alzheimer's?
Some patients with cognitive issues take a fatalistic approach toward Alzheimer's, saying an exact diagnosis is not necessary because little can be done. Currently available treatments target symptoms and often are not effective. They do not change the course of the disease.
Alzheimer's treatments may be improving. Recently reported results showed that an experimental drug called lecanemab, by Japanese drugmaker Eisai and its U.S. partner, Biogen, worked to modestly slow Alzheimer's disease. It was the first therapy to do so in a well-run trial. The Food and Drug Administration could decide whether to approve the drug as soon as January.
Recently, in a sign of the roller-coaster nature of Alzheimer's, a drug by Roche failed in clinical trials. A medication by Eli Lilly is in late-stage testing.
If a new treatment is approved by the FDA and gains Medicare coverage, blood tests could play a key role in determining who might benefit. Doctors will want to make sure patients have amyloid in their brains before prescribing the medications.
Down the road, after more research is conducted, the blood tests might be used to alert people, even those without symptoms, that they have elevated amyloid and tau in their brains, putting them at risk for Alzheimer's. Patients could start a preventive therapy early, if one exists. Or they could pursue healthier lifestyles.
"Knowing your risk can be a hugely positive motivator," said Leslie M. Shaw, a pathologist and Alzheimer's researcher at the University of Pennsylvania. "Make the changes we now know are important. Instead of being a classic couch potato, get off your duff and get going."
Even if new treatments for Alzheimer's are not cleared, many experts say, it is important for patients to know their diagnoses so they can plan for the future. Trying to hide such a diagnosis is an echo of the 1960s, when people were not told they had cancer.
"If people are having cognitive symptoms, they deserve to know their diagnosis," said Howard Fillit, co-founder and chief science officer at the Alzheimer's Drug Discovery Foundation, a nonprofit group that helps fund research into the disease. "If they test positive, they will get certainty. If they test negative, maybe they have depression or a different type of dementia that might be treated differently."
- - -
Do experts back use of the blood tests?
Many experts, even those enthusiastic about the tests, say that while they can be used carefully by certified in memory centers, there should be more research before they are used in primary-care settings. Some certified say they want more data on how the tests work for patients of different races, ethnic groups and genders.
"You want to know how the specific tests perform in different patients so you can really interpret them," said Matthew Schrag, a neurologist at the Vanderbilt University School of Medicine.
But other experts are eager to use the blood tests, saying they will help provide clarity to patients.
Demetrius M. Maraganore, chairman of the neurology department at Tulane University School of Medicine, who took part in a study sponsored by C2N, said he would start using that test immediately if it was covered by Medicare and insurance.
"The point is that patients seek an end to their diagnostic journey," Maraganore said. "This will help them to flip the page and start focusing on acceptance and getting the support they need."
- - -
Do the tests have FDA approval?
Not at this point. Under the FDA's current policy, agency approval is not required for laboratory-developed tests - which are developed and processed by a single laboratory. The current tests are those types of tests. They are regulated under the Clinical Laboratory Improvement Amendments program under the Centers for Medicare and Medicaid Services.
Still, some of the manufacturers are seeking the FDA's imprimatur, saying agency approval would assure health-care providers and insurers about the value of the tests.
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As fall temperatures set in, cold and flu season gets into full swing and holiday travel picks up, people will undoubtedly have questions about COVID-19 testing. Is this the year people can finally return to large gatherings for traditional celebrations? What role does testing play when deciding whether to go out or stay home?
Adding to the confusion are personal accounts of people who are experiencing confusing or seemingly contradictory test results.
We are part of a team that has developed and tested SARS-CoV-2 tests since the early days of the pandemic. Additionally, some of us are infectious disease specialists with decades of experience.
Our insights from both the cutting edge of rapid testing research as well as our clinical perspectives from working directly with patients can help people figure out how to make the best use of rapid tests.
Multiple negative tests, then a positive — why?
SARS-CoV-2, the virus that causes COVID-19, takes time to build up in the body, like many other viruses and bacteria that cause respiratory illness. Typically it takes two to three days to test positive after exposure. Our research group has demonstrated this, as have others.
Rapid tests detect parts of the virus that are present in the demo collected from your nose or mouth. If the virus has not replicated to a high enough level in that part of your body, a test will be negative. Only when the amount of virus is high enough will a person's test become positive. For most omicron variants in circulation today, this is one to three days, depending on the initial amount of virus you get exposed to.
Why do some people test positive for extended periods of time?
It's important to clarify which type of test we're talking about in this situation. Studies have shown that some people can test positive for a month or more with a PCR test. The reason for this is twofold: PCR tests are capable of detecting extremely small amounts of genetic material, and fragments of the virus can remain in the respiratory system for a long time before being cleared.
When it comes to rapid tests, there are reports that some people test positive for an extended period of time with the current strains of the omicron variant compared with earlier variants. Several studies show that most people no longer test positive after five to seven days from their first positive test, but between 10% to 20% of people continue to test positive for 10 to 14 days.
But why it takes longer for some people to clear the virus than others is still unknown. Possible explanations include a person's vaccination status or the ability of one's immune system to clear the virus.
In addition, a small number of people who have been treated with the oral antiviral drug Paxlovid have tested negative on rapid antigen tests, with no symptoms, only to "rebound" seven to 14 days after their initial positive test. In these cases, people sometimes experience recurring or even occasionally worse symptoms than they had before, along with positive rapid test results. People who experience this should isolate again, as it has been shown that people with rebound cases can transmit the virus to others.
Why do I have COVID-19 symptoms but still test negative?
There are several possible explanations for why you might get negative rapid tests even when you have COVID-like symptoms. The most likely is that you have an infection of something other than SARS-CoV-2.
Many different viruses and bacteria can make us sick. Since mask mandates have been lifted in most settings, many viruses that didn't circulate widely during the pandemic, like influenza and Respiratory Syncytial Virus, or RSV, are becoming common once again and making people sick.
Second, a mild COVID-19 infection in a person that's been vaccinated and boosted may result in a viral level that's high enough to cause symptoms but too low to result in a positive rapid test.
Finally, the use of poor technique when sampling your nose or mouth may result in too little virus to yield a positive test. Many tests with nasal swabbing require you to swab for at least 15 seconds in each nostril. A failure to swab according to package instructions could result in a negative test.
Our previous studies show that if you are symptomatic and do two rapid antigen tests 48 hours apart rather than just one, you are more highly likely to test positive if you are infected with SARS-CoV-2.
Do rapid tests work against the current strains of SARS-CoV-2?
Multiple studies have examined the performance of rapid tests against the omicron variant.
Fortunately, these studies show that all the rapid tests that have been authorized for emergency use by the U.S. Food and Drug Administration detect the current omicron variants just as well as previous variants such as alpha and delta. If a symptomatic person tests positive on a rapid test, they likely have COVID-19. If you are exposed to someone who has COVID-19, or have symptoms but receive a negative test, you should take another test in 48 hours. If you then test positive or if your symptoms get worse, contact your health care provider.
What's the best way to use and interpret rapid tests before gatherings?
Testing remains an important tool to identify infected people and limit the spread of the virus. It's still a good idea to take a rapid test before visiting people, especially older people and those with weakened immune systems.
If you believe you may be infected, the FDA recently updated their testing guidance largely based on data our lab collected. The testing regimen most likely to identify if you're infected is to take two tests 48 hours apart if you have symptoms. If you don't have symptoms, take three tests, one every 48 hours.
Does a positive test mean you can spread COVID to others?
The Centers for Disease Control and Prevention recommends that if you test positive for COVID-19, you should stay home for at least five days from the date of your positive test and isolate from others. People are likely to be most infectious during these first five days. After you end isolation and feel better, consider taking a rapid test again.
If you have two negative tests 48 hours apart, you are most likely no longer infectious. If your rapid tests are positive, you may still be infectious, even if you are past day 10 after your positive test. If possible, you should wear a mask. Multiple studies have shown a correlation between the time an individual tests positive on a rapid test and when live virus can be collected from a person, which is a common way to determine if someone is infectious.
Testing is still an important tool to keep people safe from COVID-19 and to avoid spreading it to others. Knowing your status and deciding to test is a decision that individuals make based on their own tolerance for risk around contracting COVID-19.
People who are older or at higher risk of severe disease may want to test frequently after an exposure or if they have symptoms. Some people may also be panic about having COVID-19 and transmitting it to others who may be at higher risk for hospitalization. When combined with other measures such as vaccination and staying home when you're sick, testing can reduce the impact of COVID-19 on all of our lives in the coming months.
Nathaniel Hafer, Assistant Professor of Molecular Medicine, UMass Chan Medical School; Apurv Soni, Assistant Professor of Medicine, UMass Chan Medical School, and Yukari Manabe, Associate Director of Global Health Research and Innovation Professor of Medicine, Johns Hopkins University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
We’ve gotten to the point in the COVID-19 pandemic where you’re probably not stressed every single day about getting the virus—the wide availability of COVID-19 vaccines and effective treatments have thankfully made that possible. And, with that, you likely have some tests around your place for the just-in-case that may have been sitting there for a while. Here’s the thing, though: They can expire. Yep, there is a COVID test expiration date printed on your package that you may not even realize is there.
Many COVID-19 tests last for just a year or so, but the odds are high that you’ll need to use your at some point. That may or may not be before the expiration date stamped on your package passes. So…do expired COVID tests work, or do you need to toss what you thought was a perfectly good test? It’s actually a little complicated. Here’s what you need to know.
Yes and no. To fully understand that, it’s important to explain how COVID-19 tests get an expiration date in the first place. “When tests are developed, the company will assess the test over time to make sure it’s performing with the quality standards intended,” says Thomas Russo, M.D., a professor and the chief of infectious diseases at the University at Buffalo in New York. “Whatever time frame they assess it for is the expiration date that will go on that test.”
This “doesn’t necessarily mean that the test won’t perform for a longer period of time,” Dr. Russo says—it’s just the amount of time that the test has been assessed for and what is authorized or approved by the Food and Drug Administration (FDA).
Older tests are more likely to have shorter expiration dates because there were time pressures to get tests out earlier in the pandemic, when they were first developed, and only so much time since they had been created to test how long they were good for, Dr. Russo says. “However, companies kept assessing the tests over time,” he says.
As a result, “many manufacturers have received shelf life extensions by the FDA,” says infectious disease expert Amesh A. Adalja, M.D., a senior scholar at the Johns Hopkins Center for Health Security.
The FDA has a list online of authorized home COVID-19 tests, along with links to “updated expiration dates” so you can check to see if your test’s expiration date has been extended.
“If you have a test and it’s ‘expired’ based on what the package says, it may or may not be the most correct expiration date,” Dr. Russo says.
Again, the expiration dates are a reflection of how long the company that manufactured the test found that it was good for—or the period of time in which they were able to assess the test. With that, there’s a chance that your test will still be good beyond the expiration date listed. “Most tests will still perform past their expiration date for several weeks,” Dr. Adalja says.
If the test has truly expired “you are more likely to get a false negative,” says Jamie Alan, Ph.D., associate professor of pharmacology and toxicology at Michigan State University. “The test might be negative because the reagents or ‘ingredients’ are past their shelf life and are not working as they should,” she explains. “They are likely good past their expiration date, although how long I cannot say with any degree of certainty.”
If you have symptoms of COVID-19 and the only test you have at home is expired, Alan says you could try it. “If you get a positive, you are probably positive,” she says. “If you get a negative, it would be good to follow up with another test, either a PCR test or another rapid at-home test.”
COVID tests contain specific reagents (aka ingredients) that react with the virus, or lack thereof, from your swab, Alan explains. “These ingredients do not work forever,” she says. “This is true for medications, lab materials, and food.”
BinaxNOW is one of the most popular home tests out there, and it typically has an expiration date stamped on the back of the box. But, again, that may not be the most up-to-date expiration date for your test.
If you have a test with an expired date on the package, check out the FDA’s list of updated expiration dates for BinaxNOW tests to see if it’s been extended. Just keep in mind that you’ll need to have your box’s lot number handy.
But, if your test is expired—both on the box and per the FDA’s updated dating—and you want to be sure you’re getting an accurate reading, Dr. Russo says it’s “probably best to not use that test.”
This article is accurate as of press time. However, as the COVID-19 pandemic rapidly evolves and the scientific community’s understanding of the novel coronavirus develops, some of the information may have changed since it was last updated. While we aim to keep all of our stories up to date, please visit online resources provided by the CDC, WHO, and your local public health department to stay informed on the latest news. Always talk to your doctor for professional medical advice.
Korin Miller is a freelance writer specializing in general wellness, sexual health and relationships, and lifestyle trends, with work appearing in Men’s Health, Women’s Health, Self, Glamour, and more. She has a master’s degree from American University, lives by the beach, and hopes to own a teacup pig and taco truck one day.
If you stocked up on at-home Covid-19 rapid antigen testing kits during one of the Omicron-variant surges, you could be in for a surprise when you bust them out for a pre-holiday test: an expiration date months in the past. According to the Food and Drug Administration, most at-home Covid-19 tests list an expiration date between four and six months from when they were manufactured.
Does that mean those expired tests no longer work? Here’s why the expiration date printed on the box isn’t as straightforward as you might expect.
The reason the answer to “when does my at-home Covid test expire?” isn’t as straightforward as, say, when the yogurt in your fridge expires has to do with the tests’ relative novelty. The tests have only been approved for two years, and crucially, the testing they underwent before hitting the market happened in just one year. If the FDA wanted to determine the maximum length of time the test was effective before putting it on the market, it would have had to delay those tests for years.
What it did instead is take a more conservative approach: authorizing a shelf-life of four to six months and then extending the expiration date as real-world data was compiled.
In an email, a spokesperson for the California Department of Public Health told Inverse that “since initial approval, most tests have had specific extensions issued by the FDA because test companies have presented information to the FDA showing the tests work well for a longer period of time.”
How can you tell if your test still works? In January of this year, the FDA released a list of updated expiration dates for different at-home rapid Covid-19 tests.
For example, BinaxNOW rapid Covid-19 tests manufactured by Abbott have been given an updated shelf life of 15 months, as have iHealth rapid tests. FlowFlex rapid tests manufactured by ACON Laboratories have been given a shelf life of 19 months. You can find a full chart of the FDA’s updated shelf-life and expiration dates for different rapid tests here.
California’s Department of Public Health has gone even further, authorizing the use of at-home rapid tests past the FDA’s extended expiration date. Their guidance now says you can use the tests as long as the control line is “both easily visible and the color specified by the specific test instructions” after the 15-minute test-development window. In other words, if you take an expired test and the control line shows up clearly, you can consider that result as valid as an at-home rapid test that isn’t expired.
A longer than initially anticipated shelf life of at-home Covid tests doesn’t mean your tests will necessarily last that long. Like medication, proper storage of Covid tests will prolong their shelf life.
If the test is exposed to very hot or cold temperatures, it will degrade faster than if it’s kept at more stable temperatures. According to the FDA, “test performance may be impacted if the test is used while it is still cold, such as being used outdoors in freezing temperatures or being used immediately after being brought inside from freezing temperatures, or in a hotter than expected environment, such as outside in the summer.”
To perform as expected, manufacturers assume the test is being performed in an environment that is roughly between 59 and 86 degrees Fahrenheit. If the test is delivered to you when it’s very hot or cold outside, the FDA advises bringing the test inside and leaving it at room temperature for at least two hours before using it.
If you’re not sure if the test is still good, the FDA suggests taking the test. “As long as the test line(s) appear as described in the instructions, you can be confident that the test is performing as it should. If the line(s) do not appear in the correct location(s) and within the correct time as shown in the test instructions when you perform the test, then the results may not be accurate, and a new test is needed to get an accurate result,” the FDA explains.
Nate Hafer is the director of operations for the University of Massachusetts Center for Clinical and Translational Science and an assistant professor in molecular medicine at UMass Chan Medical School. He tells Inverse that the extended expiration dates make sense to him, especially in light of how the tests work.
After you swab your nostrils, you put the swab in a solution that breaks apart the demo so different proteins in the demo can be detected. In the case of rapid antigen tests, the protein they’re looking for is called the nucleocapsid protein, which is “one of the most abundant proteins in the SARS-CoV-2 virus,” Hafer says.
Once the solution has broken apart the genetic material, you put a few drops of the solution on the test strip. The strip has been painted with antibodies that, if they come into contact with the nucleocapsid protein, will change color. As the solution moves down the paper, the control line will appear regardless of whether it detects the nucleocapsid protein or not.
The various substances used in the test are fairly stable, Hafer says, which is why the tests last past the expiration date if stored properly. If they are exposed to prolonged heat or cold, Hafer says both the solution and the antibodies on the test paper could degrade.
“I would guess that the antibodies on the strip of paper are one of the more sensitive things that could be damaged by extreme heat or cold, but the solution probably has some chemicals in it that could also be influenced by extreme temperatures,” he says.
So if you come across an expired at-home test, don’t immediately throw it away. Hang on to it and the next time you need to test, make sure the control line shows up as it should. If it does, go ahead and treat it like a non-expired test. If that line looks funky, head to the store for a new one.