With COVID cases continuing to rise across Illinois and parts of the U.S. and tests widely available, many are wondering if their results are accurate, if they are reading them properly and how often they should test.

Here's a breakdown of some of the most-asked questions surrounding COVID testing and what experts are saying.

Regardless of symptoms or vaccinations, those who are exposed to someone with coronavirus should get tested at least five days after their exposure.

Those who develop symptoms should get tested as symptoms develop, but if a test is negative and symptoms persist another test might be needed a few days later, particularly for those who use at-home test kits.

According to the Centers for Disease Control and Prevention, "positive results from self-tests are highly reliable."

Full coverage of the COVID-19 outbreak and how it impacts you

Negative results, however, may not rule out infection, particularly in those with COVID-19 symptoms, the CDC states.

"If it's positive, it's positive, like we don't worry about false positives," Chicago Department of Public Health Commissioner Dr. Allison Arwady said just before Memorial Day.

Arwady noted that in some cases, a negative test could be because levels of viral load may be lower, "and the chance of you spreading it it lower, but it's not zero."

According to the Mayo Clinic, "the risk of false-negative or false-positive test results depends on the type and sensitivity of the COVID-19 diagnostic test, thoroughness of the sample collection, and accuracy of the lab analysis."

The CDC recommends those who test negative, test again 24-48 hours after their first test.

"Consider repeating the test 24 to 48 hours later," the guidance states. "Multiple negative tests increases the confidence that you are not infected with the virus that causes COVID-19."

Those who test positive using an at-home test are asked to follow the latest CDC guidelines and communicate the results to their healthcare provider.

But that process is likely not happening with many at-home COVID tests.

The at-home results are part of the reason Illinois' health department changed the COVID metrics it tests.

With the state no longer reporting COVID case and test positivity, health officials said the reason is in part due to incomplete data due to at-home tests.

The department said the change, in part led by the fact that national testing data does not often reflect results from at-home tests, means that labs will no longer be required to report negative rapid antigen test results, though they will still need to show negative PCR and nucleic acid amplification test results.

While PCR tests can be more effective at detecting the virus, some people who contract COVID-19 can have detectable virus for up to three months, though that doesn't mean they are contagious.

When it comes to testing, the PCR tests are more likely to continue picking up the virus following infection.

"PCR is very unusual for it to remain positive, especially for 90 days. It can remain positive for 10 days, 20 days, but in most cases, it doesn't say positive that long and even, you know, 90 days would be the very slight edge that we're seeing," Arwady said.

"A positive PCR does not mean that you are still contagious," she added. "It's very, very sensitive. So it means you've had COVID. You either have it now or it's still picking up traces."

The CDC notes that tests "are best used early in the course of illness to diagnose COVID-19 and are not authorized by the U.S. Food and Drug Administration to evaluate duration of infectiousness."

According to the CDC, "a specimen that is not collected correctly may lead to false or inconclusive test results."

According to the U.S. Food and Drug Administration, the line indicating a positive test "can be very faint."

"Any pink/purple line visible here indicates a positive result," the FDA states.

Still, experts say "if you or the telehealth proctor disagree on the presence of a faint line and/or the presence of a line is uncertain, additional confirmatory testing should be conducted."

First, you'll need to know the difference between whether you must quarantine or isolate. Those who believe they have been in contact with someone who has COVID and are unvaccinated should quarantine. Those who test positive, regardless of vaccination status, must isolate, according to the CDC.

Close contact is defined by the CDC and the Illinois Department of Public Health as "someone who was less than 6 feet away from an infected person for a cumulative total of 15 minutes or more over a 24-hour period."

If you come into close contact with someone with COVID-19, you should quarantine if you are not up-to-date on COVID-19 vaccines or are unvaccinated. For these individuals, the CDC and IDPH recommend you:

Those who are close contacts of someone with COVID but are up-to-date on their vaccinations or have had a confirmed case of COVID-19 within the last 90 days do not need to quarantine, but the CDC does recommend they wear a well-fitting mask around others for 10 days after their most recent exposure and get tested after at least five days.

According to the CDC, people who are positive for COVID should stay home until it's safe for them to be around others, including even other members of their home.

Health officials recommend a "sick room" or area for those who are infected and a separate bathroom, if possible.

But isolation may not just be for those who test positive. The CDC also recommends those who have symptoms of COVID-19 and are awaiting test results or have not yet been tested isolate, "even if they do not know if they have been in close contact with someone with COVID-19."

How do you end isolation?

So how do you calculate your isolation period?

According to the CDC, "day 0 is your first day of symptoms." That means that Day 1 is the first full day after your symptoms developed.

For those who test positive for COVID but have no symptoms, day 0 is the day of the positive test. Those who develop symptoms after testing positive must start their calculations over, however, with day 0 then becoming the first day of symptoms.

Under the CDC guidance, those in isolation should:

While testing out of isolation is not required, the CDC says those who choose to should use an antigen test and not a PCR test. These can be taken toward the end of the isolation period.

"Collect the test sample only if you are fever-free for 24 hours without the use of fever-reducing medication and your other symptoms have improved," the CDC states. "If your test result is positive, you should continue to isolate until day 10. If your test result is negative, you can end isolation, but continue to wear a well-fitting mask around others at home and in public until day 10."

The federal government is now offering residents double the number of free COVID rapid antigen tests during its newest round of kit availability, so how can you get yours?

In previous rounds of test distributions residents could only claim up to four per household, but residents can now request up to eight of the tests, which will be shipped for free to their residences, according to the United States Postal Service.

You can sign up via the USPS website here.