How effective are at-home tests against the omicron variant?

Posted at 9:37 PM, Dec 29, 2021
and last updated 2021-12-30 07:41:38-05

(WXYZ) — Before Christmas gatherings, many families may have relied on at-home COVID tests to keep everyone safe. However, negative results don’t always mean COVID isn’t crashing the party.

“The problem with the at-home tests is that the false negativity rate is about 20%,” said Dr. Asha Shajahan, Medical Director of Community Health at Beaumont Grosse Pointe. “Just going by one home test, since the false negative rate is so high, it could falsely mislead you to believing you’re negative when actually you are positive."

That would mean roughly 2 out of every 10 negative at-home test results are actually positive, and when it comes to the omicron variant, that number may be even higher.

"Per the FDA, as of right now they say most of the at-home tests do accurately detect omicron, but the sensitivity might be slightly lower,” Dr. Shajahan said. “Most likely it might be a higher (false negative) rate with omicron, but we have yet to see as more tests come out.”

As Dr. Shajahan mentioned, this week the FDA announced that some at-home tests appear not to be as sensitive to the omicron variant, leading to more false negative results.

“In some of the tests, there appears to be somewhat of a diminution, not a disappearance, but a diminution of the sensitivity,” said Dr. Anthony Fauci during a White House Teleconference on Wednesday.

However, during that teleconference Dr. Fauci reiterated these tests, which are more convenient and cost effective, can still detect omicron and the use of them is still encouraged.

"The fact that the sensitivity is diminished somewhat does not obviate the importance of the still advantage and usefulness of these tests under different circumstances,” Dr. Fauci said. “That was the message of the FDA. They wanted to make sure they were totally transparent in saying the sensitivity might come down a bit, but they did emphasize there still is an important use of these tests."

According to Dr. Shajahan, the at-home tests are more accurate when you’re symptomatic, and are tested over multiple days. That’s because these tests measure for antigens.

“The antigen test is actually testing your immune response to the virus and it’s a one time immune response that it’s testing," Dr. Shajahan said. "Whereas the molecular test, which is what the PCR test is, does viral replication. So it tests it multiple times so it's more accurate of a test.”

For that reason, Dr. Shajahan recommends PCR tests if you want to be absolutely certain, and with extremely high demand for PCR tests, she encourages patients to plan ahead.

"If you are worried about infecting a family member of a friend or attending a gathering, the best thing to do is get a PCR test if you can," Dr. Shajahan said. “I know it's a lot more inconvenient than the home test, but better safe than sorry."