covid test

What to Know About COVID Tests: Accuracy, Inconclusive Results, Faint Lines and More

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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.

When Should You Get a COVID Test?

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.

How Accurate Are At-Home COVID Tests?

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

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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."

What If You Test Positive Using an At-Home Test?

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.

How Long Can You Test Positive for COVID Following Infection?

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."

What If Your Test Results Are Inconclusive?

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

What If the Positive Line is Very Faint?

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."

How Long Should you Quarantine or Isolate?

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."

Here's the breakdown:

Quarantine

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:

  • Stay home and away from other people for at least 5 days (day 0 through day 5) after your last contact with a person who has COVID-19. The date of your exposure is considered day 0. Wear a well-fitting mask when around others at home, if possible.
  • For 10 days after your last close contact with someone with COVID-19, watch for fever (100.4◦F or greater), cough, shortness of breath, or other COVID-19 symptoms.
  • If you develop symptoms, get tested immediately and isolate until you receive your test results. If you test positive, follow isolation recommendations.
  • If you do not develop symptoms, get tested at least 5 days after you last had close contact with someone with COVID-19.
    • If you test negative, you can leave your home, but continue to wear a well-fitting mask when around others at home and in public until 10 days after your last close contact with someone with COVID-19.
    • If you test positive, you should isolate for at least 5 days from the date of your positive test (if you do not have symptoms). If you do develop COVID-19 symptoms, isolate for at least 5 days from the date your symptoms began (the date the symptoms started is day 0). Follow recommendations in the isolation section below.
    • If you are unable to get a test 5 days after last close contact with someone with COVID-19, you can leave your home after day 5 if you have been without COVID-19 symptoms throughout the 5-day period. Wear a well-fitting mask for 10 days after your date of last close contact when around others at home and in public.
    • Avoid people who are have weakened immune systems or are more likely to get very sick from COVID-19, and nursing homes and other high-risk settings, until after at least 10 days.
  • If possible, stay away from people you live with, especially people who are at higher risk for getting very sick from COVID-19, as well as others outside your home throughout the full 10 days after your last close contact with someone with COVID-19.
  • If you are unable to quarantine, you should wear a well-fitting mask for 10 days when around others at home and in public.
  • If you are unable to wear a mask when around others, you should continue to quarantine for 10 days. Avoid people who have weakened immune systems or are more likely to get very sick from COVID-19, and nursing homes and other high-risk settings, until after at least 10 days.
  • Do not travel during your 5-day quarantine period. Get tested at least 5 days after your last close contact and make sure your test result is negative and you remain without symptoms before traveling. If you don’t get tested, delay travel until 10 days after your last close contact with a person with COVID-19. If you must travel before the 10 days are completed, wear a well-fitting mask when you are around others for the entire duration of travel during the 10 days. If you are unable to wear a mask, you should not travel during the 10 days.
  • Do not go to places where you are unable to wear a mask, such as restaurants and some gyms, and avoid eating around others at home and at work until after 10 days after your last close contact with someone with COVID-19.

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.

Isolation

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?

  • You can end isolation after five full days if you are fever-free for 24 hours without the use of fever-reducing medication and your other symptoms have improved (Loss of taste and smell may persist for weeks or months after recovery and need not delay the end of isolation​).
  • If you continue to have fever or your other symptoms have not improved after 5 days of isolation, you should wait to end your isolation until you are fever-free for 24 hours without the use of fever-reducing medication and your other symptoms have improved. Continue to wear a well-fitting mask through day 10. Contact your healthcare provider if you have questions.
  • Do not go to places where you are unable to wear a mask, such as restaurants and some gyms, and avoid eating around others at home and at work until a full 10 days after your first day of symptoms.

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:

  • Monitor your symptoms. If you have an emergency warning sign (including trouble breathing), seek emergency medical care immediately.
  • Stay in a separate room from other household members, if possible.
  • Use a separate bathroom, if possible.
  • Take steps to improve ventilation at home, if possible.
  • Avoid contact with other members of the household and pets.
  • Don’t share personal household items, like cups, towels, and utensils.
  • Wear a well-fitting mask when you need to be around other people.

Do You Need to Test Out of Isolation?

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."

How to Get Your Free COVID Test Kits From the Government

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.

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