FDA: Rapid Antigen Tests May Be Less Effective at Detecting Omicron

Rapid antigen tests whitethorn beryllium little delicate astatine detecting the highly contagious omicron variant and could pb to results that are "false negative," the Food and Drug Administration said Tuesday.

Preliminary probe by the FDA, successful collaboration with the National Institutes of Health's Rapid Acceleration of Diagnostics program, utilized samples from patients confirmed to beryllium infected with the omicron strain of the microorganism to survey the show of at-home tests, besides known arsenic "antigen" tests.

The bureau said aboriginal information suggests that antigen tests "do observe the omicron variant but whitethorn person reduced sensitivity," meaning it's imaginable specified tests could miss an infection.

Previous investigating by RADx focused connected heat-inactivated microorganism samples, which are diligent specimen confirmed to beryllium infected with the omicron variant that person been heat-treated truthful that the microorganism is nary longer live. Currently disposable antigen tests were capable to observe the mutated strain "with akin performance" to different variants successful that study. But, the bureau notes that unrecorded microorganism is the champion mode to measure existent trial performance, portion "heat-inactivated samples are the champion disposable enactment erstwhile diligent samples with unrecorded microorganism are not available."

The FDA stopped abbreviated of telling radical to debar utilizing antigen tests and did not specify the brands of tests utilized successful the study. The bureau besides emphasized the findings are based connected laboratory information and not the much reliable objective survey evaluations, which are presently ongoing.

"The FDA continues to authorize the usage of these tests arsenic directed successful the authorized labeling and individuals should proceed to usage them successful accordance with the instructions included with the tests," the bureau said successful a statement. "Antigen tests are mostly little delicate and little apt to prime up precise aboriginal infections compared to molecular tests."

The caller findings travel arsenic lawsuit numbers are surging crossed state astatine a clip erstwhile household and friends seeking to stitchery implicit the holidays, person clamored for over-the-counter antigen tests to diagnose infections owed to agelong lines for PCR tests — which are amended astatine detecting debased levels of the microorganism — and delayed turnaround times for their laboratory results.

But, the CDC said Wednesday that less than 1% of the U.S. COVID-19 cases genetically sequenced past week were the omicron variant; the delta variant accounted for much than 99%, reducing concerns astir presently authorized antigen tests missing an infection. It comes a time aft the bureau importantly slashed estimates of the percent of caller cases linked to the omicron variant.

The CDC had antecedently reported the omicron variant comprised 73% of each cases for the week of Dec. 18. But connected Tuesday, the bureau revised that fig to 22.5%, suggesting that portion the caller variant was connected the rise, delta — which is the much terrible strain — is inactive a driving unit down the existent surge. The astir caller study estimates that arsenic of Dec. 25, 59% of each U.S. infections were caused by omicron, a fig that volition apt beryllium amended aft much information from familial sequencing is processed.

Rapid antigen tests, which enactment by detecting aboveground proteins of the coronavirus, are comparatively inexpensive and quick, with results known successful astir 15 minutes. They can, however, miss the aboriginal stages of COVID-19 infection. Most fashionable at-home tests counsel users to instrumentality 2 tests connected abstracted days to guarantee much close results.

In an interrogation with NBC's "TODAY" show, CDC Director Dr. Rochelle Walesnky said portion antigen tests whitethorn not execute arsenic good arsenic it did for different variants, "it's inactive picking up rather a spot of infection" and the bureau encourages its use.

"They are a truly really adjuvant tool," Walensky said. "But what we would reiterate, and is besides successful our guidance, is that if you person a antagonistic antigen trial and you person symptoms, past you should spell up and get that PCR test. And those antigen tests are truly adjuvant for things similar investigating to enactment successful school, wherever we’re getting an antigen trial each day, oregon each different day, oregon wherever they’re utilizing them successful higher acquisition to surface students each respective days, that’s wherever they execute truly rather well, arsenic well."

The FDA recommends that if a idiosyncratic tests antagonistic connected an antigen trial but has symptoms of COVID-19 oregon has a “high likelihood of corruption owed to exposure,” they should follow-up with a molecular PCR trial to corroborate the result. A idiosyncratic who tests affirmative with an antigen test, should self-isolate and question follow-up attraction with a wellness attraction supplier to find the adjacent steps, the bureau said.

Earlier this month, the White House announced the Biden medication would administer 500 cardinal accelerated COVID-19 tests to U.S. households for escaped starting successful January. 

As cases surge successful galore parts of the state owed to the dispersed of the Omicron variant of the coronavirus, the CDC changed its guidelines for erstwhile vaccinated and unvaccinated radical tin instrumentality to enactment aft an exposure. LX News Now Host Eric Alvarez explains wherefore the alteration was made and what you request to know.