Antibody Tests Positive For 27 Percent In Harlem: New Data

HARLEM, NY — Almost 27 percent of Harlem residents tested for antibodies showed signs that they were previously infected with the coronavirus that causes COVID-19, according to new city data.

Of the 65,4832 residents tested in the eight ZIP codes that make up the neighborhood, roughly 26.7 percent tested positive, according to data released by the Department of Health on Tuesday.

The ZIP code with the highest rate of positive tests was 10031, which includes parts of West Harlem and Hamilton Heights. About 32.7 percent of antibody tests came back positive for residents in that area.

Harlem's lowest rate of positive tests was in the 10026 ZIP code, covering the area just north of Central Park, where about 22.2 percent of residents' tests came back positive.

Citywide, Manhattan had the lowest rate of positive tests out of all five boroughs, with about 19 percent of tests coming back positive. The Bronx had the highest rate, at about 33 percent.

Percent positive antibody tests by Harlem ZIP code:

• 10026: 22.2 percent (7,309 tested, 1,622 positive)
• 10027: 22.9 percent (11,306 tested, 2,590 positive)
• 10029: 25.3 percent (13,273 tested, 3,364 positive)
• 10030: 26.6 percent (4,839 tested, 1,286 positive)
• 10031: 32.7 percent (13,496 tested, 4,408 positive)
• 10035: 28.1 percent (6,258 tested, 1,759 positive)
• 10037: 26.6 percent (4,271 tested, 1,137 positive)
• 10039: 27.9 percent (4,730 tested, 1,318 positive)
• Total: 26.7 percent (65,482 tested, 17,484 positive)

The antibody tests, or serology tests, indicate whether a person may have been exposed to the coronavirus by measuring their bloodstream for signs that their immune system produced proteins, called antibodies, to fight off the virus.

Mayor Bill de Blasio announced Tuesday that the city's website for coronavirus data would start including the results of antibody tests, but experts warn that such data should be taken with a grain of salt.

First, antibody test results aren't always accurate.

Positive tests results could mean the person has antibodies from an infection with a virus in the same family as the coronavirus, according to the U.S. Centers for Disease Control and Prevention. The chance of receiving a false negative can be as high as 30 percent, depending on when the test is conducted, according to a Harvard Medical School blog post.

The data also may not accurately reflect the prevalence of antibodies among all neighborhood residents or New York City residents, because people who have been ill with COVID-19 symptoms or were exposed to the virus may be likelier to seek out antibody testing, the city wrote in a disclaimer about the dataset.

"We will be the first jurisdiction in the nation to present our antibody data this way," de Blasio told reporters. "While there is still much to learn about the science of COVID-19 antibody testing, it is an important element to consider when understanding the epidemiology of COVID."

Patch reporter Maya Kaufman contributed to this report.