Clarify the Role of Home Tests for COVID-19

Patients will ask about HOME antigen tests for COVID-19...now that OTC BinaxNow, Ellume, and QuickVue are in stores and online.

These viral tests use a nasal sample...give results in about 15 minutes...and are for patients age 2 and up with or withOUT symptoms.

BinaxNow or QuickVue shows results similarly to an at-home pregnancy test. Either costs about $20 to $30 for a box of 2 tests.

Ellume requires smartphone access...to walk patients through performing the test and reporting results. It costs about $40/test.

Expect the biggest role for these home tests to be in patients who are UNvaccinated or not fully vaccinated...for peace of mind.

For example, parents may want to test a child before visiting grandparents...to check that allergy symptoms aren't due to COVID-19.

But point out that a negative home test may not be accepted for travel, attending events, etc. Advise to check before buying.

Help patients understand limitations of test results.

During the height of the pandemic, false NEGATIVES were the concern...since antigen test sensitivity can be below 80%.

Now false POSITIVES may be an issue, especially in patients withOUT symptoms...even with antigen tests reported to be highly specific.

That's because the likelihood a patient with a positive test truly has COVID-19...the positive predictive value (PPV)...depends on local COVID-19 prevalence, which is currently 3% or less in many areas.

For instance, BinaxNow is labeled 85% sensitive and 99% specific. Plugging in 3% prevalence results in a PPV of 72%...so about 30% of patients who test positive may NOT have COVID-19.

Check your health dept website for local prevalence estimates.

Advise patients withOUT symptoms that they can generally trust negative results...or positive results if they DO have symptoms.

But usually recommend a confirmatory PCR test when results don't turn out as expected...if antigen test results conflict...or for persistent symptoms despite 2 negative antigen tests.

Emphasize the importance of following test directions "to the letter"...to help make results as accurate as possible.

Access our chart, COVID-19 Point-of-Care Testing, to compare at-home tests with the tests your pharmacy may offer.

Key References

  • www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html#evaluating-test-results (5-21-21)
  • www.fda.gov/medical-devices/coronavirus-disease-2019-covid-19-emergency-use-authorizations-medical-devices/in-vitro-diagnostics-euas-antigen-diagnostic-tests-sars-cov-2 (5-21-21)
  • www.cdc.gov/coronavirus/2019-ncov/testing/self-testing.html (5-21-21)
Pharmacist's Letter. June 2021, No. 370603



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