The margin of error with the flu test you typically receive at your doctor’s office just got significantly smaller, thanks to a U.S. Food and Drug Administration (FDA) action that went into effect last month.
The type of rapid flu test you might typically receive at a doctor’s office or clinic checks for virus antigens by way of a throat or nasal swab. Six of these tests from various manufacturers meet the new standards, according to the FDA, and those that don't can no longer be sold.
Not that this matters much for your own course of care — assuming your doctor follows current guidelines from the Centers for Disease Control and Prevention. The CDC says clinicians shouldn't necessarily rely on or wait for the results of such rapid flu tests, which come in about 15 minutes, to determine how to treat patients who show up with something like a cough and fever during influenza season. Rather, the CDC says clinicians should use their discretion to prescribe antivirals right away, based on their evaluation of flu-like symptoms alone.
Part of the reason for this advice has been the tests’ overall unreliability — in giving false negatives and, to a lesser extent, false positives.
The FDA found evidence that rapid tests had contributed to deaths through false negative results. The tests failed to find proof of the flu in people who really did have it — a dangerous error especially for young children or older adults who suffer more severe complications. It remains to be seen whether the treatment advice will change now that the tests must have a lower margin of error.
Where the rapid flu tests might be especially helpful, according to the CDC, is in institutional settings such as nursing homes or on cruise ships, where officials need to get a quick handle on whether an outbreak they are just seeing is potentially the flu.