Antigen tests are indeed “game-changers” but in a bad way
Updated: Aug 15, 2021
On the subject of antigen testing, Elon Musk is not wrong.
The colorful Tesla CEO recently had symptoms of Covid-19 and underwent at least 4 tests for the presence of the disease. He had multiple antigen tests with 2 positive and 2 negative tests before reports widely disseminated that he was frustrated with the testing calling them "extremely bogus." Having mild symptoms, he reportedly also then had a PCR test that confirmed he was indeed positive.
Without knowing the sequence and intervals between his tests, it is difficult to pinpoint why Mr. Musk had multiple discrepant tests. We also do not know if he was employing the tests properly and for the intended indication. Nonetheless, the conflicting tests taken within a short time frame provide no reassurance that antigen tests can be relied upon as diagnostic tests for people with mild symptoms (or any combination of symptoms for that matter).
Currently 6 point-of-care tests have been approved for EUA including the BinaxNow from Abbott whose particularly vaunted test received $750M from the federal government for 150 million tests. Importantly, all these antigen tests were approved under emergency use authorization (EUA) for symptomatic patients within 7 days of having initiation of symptoms. Unfortunately, many “experts” and public health officials were quick to point out the greatness of these tests, without acknowledging this weakness. After the approval of multiple antigen tests including those from Becton Dickinson, Quidel, and Abbott, many people jumped on the bandwagon. The approved antigen test from Quidel “is a real game changer," gushed Dr. Scott Gottlieb in May.
Statements like this from respected authorities who do not qualify the merits and detriments of the test (ALL tests have these) and fail to detail on the circumstances where the test should be properly used actually can make the tests harmful. Individuals undergo the test and become personally convinced of the verity of the result and then act differently than if they did not have the test. Instead of being used as a rapid cheap test for symptomatic individuals with high viral loads, they are being used for asymptomatic screening. (To understand fully the widespread love for this test, just Google “game changer” and “Abbott.”)
The off-label use of antigen tests is doing major damage and destroying any niche value they may carry.
To appreciate fully the incredible misuse of the antigen tests, one need look no further than the seat of the Executive Branch of the United States government, the White House in Washington DC. For the acknowledged super spreader event at the Rose Garden on September 26, an antigen test was found to be the screening test for the individuals who attended. There has been no public reporting on whether everyone was tested and when. It is also unclear if individuals had a single test or multiple tests. or whether active symptoms were monitored. What is apparent is that everyone present was convinced, probably due to antigen testing, that no one there carried a communicable illness.
The false sense of security created by the antigen tests led to their spectacular failure.
Proponents of antigen tests claim that a single test is not its core strength but that multiple cheap tests hasten its value. This school of thought also claim that daily universal testing is the way out of the pandemic. With multiple tests, the possible lack of sensitivity of the antigen tests would be offset by the frequency of their administration.
The federal government was certainly on board with this philosophy as it bought 150 million Abbott tests. One area of use for these tests was to be nursing homes. Astoundingly, the HHS contradicted its own branch, the FDA, by rolling out the tests to asymptomatic patients in this population while using them for diagnostic clinical care and screening.
While nursing homes were thought to benefit the most from antigen testing, this idea has not been shown. After the initiation of disseminated use to these facilities in Nevada, public officials found 60% of the tests to be inaccurate. To prevent further erroneous readings, the state of Nevada stopped using the tests as the officials found the results were more confusing than the information the tests provided.
Interestingly, false negatives were thought to be the main shortcoming of the antigen test. However, widespread use has revealed that false positives are also an issue. An “outbreak” in Manchester, VT was found to be potentially the result of simply flawed antigen tests when numerous individuals tested positive by these tests and negative by PCR tests.