City health officials warn coronavirus antibody tests may not prove immunity

New York City health officials are advising medical providers against using antibody tests to determine coronavirus infections or potential immunity.

The serological tests, as they’re called, are too unreliable and it’s not yet known whether the detection of antibodies translates to immunity from COVID-19, according to a letter dated April 22 from Demetre Daskalakis, a deputy commissioner at the city Health Department.

“They may produce false negative or false positive results, the consequences of which include providing patients incorrect guidance on preventive interventions like physical distancing or protective equipment,” Daskalakis wrote in the letter.

With so many uncertainties around asymptomatic carriers of the virus and how many people have truly been infected, attention has turned to antibody testing in hopes it can help shed light on who has actually caught the bug and whether they are now immune.

Daskalakis warned medical providers shouldn’t assume any of the tests now being marketed are “reliable enough for use in routine clinical practice” and that some are falsely claiming they’ve been approved for use by FDA.

“Dose of reality folks,” said Councilman Mark Levine (D-Manhattan), the chair of the Council’s health committee, who shared the letter on social media Thursday night.

“There is some irrational exuberance on antibody tests,” Levine tweeted. “They are useful for tracking trends in the general population, but should *not* be used to make personal health decisions.”

Levine added though that the tests still have a purpose in the fight against the pandemic.

“Anti-body tests do, however, remain extremely useful to determine whether volunteers can donate plasma to patients still battling covid,” he said.

The serological tests are unreliable in diagnosing viruses because the antibody response may take days or weeks to be detectable, meaning someone who was recently infected might still test negative, according to the city.

The letter was sent just a day before the state announced preliminary results from its own antibody study showing 2.7 million New Yorkers may have been exposed to coronavirus.

Gov. Andrew Cuomo s pressing for more widespread antibody testing, believing it to be a key to restarting the economy because it would indicate which workers may have acquired some immunity to the bug.

But others, like White House coronavirus expert Dr. Anthony Fauci, have cautioned against reading too much into the tests at this point, in part due to the same reasons noted by the city.

“There’s an assumption — a reasonable assumption — that when you have an antibody that you are protected against reinfection, but that has not been proven for this particular virus. It’s true for other viruses,” he said earlier this week.

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