Antigen false negative alarm as COVID self-tests roll in

There are concerns in the medical field about the accuracy of COVID-19 tests being conducted by private facilities as well as suggestions that false negatives are being arrived at because of poor technique.

The issue came to the fore on Wednesday via social media, but Minister of Health and Wellness Dr Christopher Tufton has indicated that this is not as grave as is being put forward.

One medical doctor, Kim Johnson, has claimed that the issue is causing chaos, referencing the practice of “merely tickling the nostril”, especially when administering an antigen test, as a “recipe for disaster”.

Antigen tests are predominantly being administered by private facilities locally.

The accuracy of antigen tests, in general, is varied, and is less precise than the polymerase chain reaction model, which is regarded as the gold standard. Some studies indicate that the accuracy of antigen tests could be as low as 60 per cent when self-administered.

Anxiety about precision may heighten as Jamaica prepares to roll out as many as 150,000 home self-test kits across the country.

“There will always be margins of error in the test kits as well as the administration,” Tufton said when the issue was put to him by The Gleaner on Wednesday.

“We need to keep [this] to a minimum, and that’s based on proper training and monitoring,” he added.

Five thousand self-administered tests have been distributed within the hotel sector, and there are plans for thousands more to go to schools and other key sectors of the economy.

Opposition Spokesman on Health Dr Morais Guy said on Wednesday that the accurate administration of the test by private facilities is only one of several issues being encountered in the medical field.

The others, he said, involve the validity of tests being imported into the island as well as the allowance of self-administered tests.

“If the tests are going to be self-administered, then we have a challenge,” said Guy.

He said both the nasal and throat swabs, if done accurately, have been proven to be difficult to endure, suggesting that self-administration may prove to be even more difficult.

“You are going to miss quite a lot of those who are positive, but if the instructions are followed and done in a specific window, then there can be better results,” he said.

Limited window

Guy said that while PCR tests are able to detect the virus in asymptomatic people, antigen tests have a limited window and usually record positive results from the first sign of symptoms to approximately five days after.

He said that ideally, sampling should be done on day three.

“I suspect that a lot of the false negatives are coming in because some people wait too long after that window. Even though they have symptoms, they go and they test and the test comes back negative because there’s no longer that window of opportunity to test the antigen, hence the complaint about the results,” said Guy, a medical doctor.

“It’s more the results of the testing as opposed to how it is actually sampled,” he said, adding that that is where “the major problem lies”.

Medical Association of Jamaica President Dr Brian James said there is “no significant mistrust” on his part of the self-administered tests, pointing out that they have been approved by the World Health Organization (WHO).

He said, however, that there may be a support structure to assist self-test users with instructions and recommendations.

“Certainly, when the WHO does approval for the test, they validate it against standards, whether the PCR or others, and they check it to make sure that these are things that can be used for the purpose that they were meant to be used. So I wouldn’t have any significant mistrust of it,” he said.