When and How to Test Yourself: Israel Fine-tunes Antigen Instructions

When exposed to a COVID carrier, people should take more than one test or at least wait three days since exposure before testing with rapid kits, top Israeli health official says

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Medical staffer hold a rapid COVID test at a test center in Jerusalem.
Medical staffer hold a rapid COVID test at a test center in Jerusalem.Credit: Emil Salman

People self-testing for COVID-19 should swab their throat as well as their nose when using rapid antigen kits to increase the chances of detecting the omicron variant, a top Israeli health official said on Monday.

The recommendation goes against the advice of the U.S. Food and Drug Administration, which has said manufacturers' instructions should still be followed and that any incorrect use of throat swabs could pose a safety risk.

On Israeli Army Radio, Sharon Alroy-Preis, Israel's public health chief, said antigen tests, used widely in the country, are less sensitive than PCR tests in detecting illness. “In order to increase their sensitivity we will from now on recommend swabbing the throat and the nose. It's not what the manufacturer instructs, but we are instructing this,” she said.

The Health Ministry did not immediately respond when asked if it has checked throat swabs using nasal test kits work and whether it has sought advice from the manufacturers.

With omicron pushing daily infection cases to record highs, Israel's testing centers have been struggling, prompting health officials to prioritize risk groups for PCR testing and trust younger, vaccinated people to test at home if exposed to a carrier.

People line up to get rapid COVID tests in Jerusalem Credit: Emil Salman

Last week the Health Ministry revised its testing policies due to the spike in people exposed to the virus. The ministry began allowing unvaccinated people exposed to an infected person to undergo a quick antigen test, instead of a PCR test, in order to be released from quarantine.

More than one test

Alroy-Preis said that when exposed to a carrier, people should take more than one test or at least wait three days since exposure before testing with rapid kits.

The Health Ministry later issued a clarification, saying that "there is no instruction to self-isolate during these three days," but rather to "take personal responsibility by wearing masks, maintaining social distance, avoiding crowds."

The ministry added that those "showing any symptoms should get tested immediately."

Rapid COVID tests at a testing center in HaderaCredit: Ilan Assayag

Some infectious disease experts have advocated throat swabbing with antigen tests because people can already transmit omicron to others when it has infected their throat and saliva but before the virus reaches their nose.

A study released on Wednesday on medRxiv before peer review looked at 29 omicron-infected workers in high-risk professions who had PCR and antigen tests done simultaneously on multiple days.

The PCR tests of saliva detected the virus on average three days before rapid nose-swab samples became positive.

But the FDA tweeted on Friday: “when it comes to at-home rapid antigen COVID-19 tests, those swabs are for your nose and not your throat.” Throat swabs, it said, “if used incorrectly, can cause harm to the patient.”

Israel has confirmed around 1.5 million infections since the pandemic began and more than 8,000 deaths. Around 60 percent of its 9.4 million population is fully vaccinated, Health Ministry data shows.

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