A doctor holds up an antibody test kit at a...

A doctor holds up an antibody test kit at a drive-thru testing site in Hempstead on April 14. Credit: AP/Seth Wenig

You've been hearing a lot about antibody testing these days. Here's what you need to know about it:

What is a coronavirus?

Coronaviruses are named for their crown-like spikes. They circulate among pigs, bats, cats and other animals. Seven out of hundreds are known to affect humans, including the virus that causes COVID-19.

What is an antibody?

Antibodies are essentially germ fighters. The immune system produces them to attack and neutralize viruses and bacteria that cause illnesses.

How do antibodies work?

The Y-shaped proteins can block coronavirus spikes from invading a cell and herd the invaders together to decrease their ability to do damage.

What is an antibody test?

The blood tests conducted by New York and others measure the level of antibodies produced to fight the coronavirus. Most COVID-19 patients develop some detectable antibodies, but the level varies.

What can an antibody test tell us?

For an individual, the antibody test has been likened to a look through the rearview mirror. It tells you if you had the COVID-19 virus and fought it off.

Does a positive antibody test mean a person has immunity?

Many scientists believe that antibodies confer at least some immunity, but how much and for how long is under study.

What will wide-scale antibody testing reveal?

Testing programs of the kind rolled out by New York State can reveal what percentages of the population had the disease, including people who recovered without showing any symptoms. The testing can also show what percentage did not have the disease and could be susceptible.

Why is it important to know how widely the disease has spread?

The more people who have had the disease, the harder it becomes for the virus to find people to infect. A high enough number indicates “herd immunity” in a community at large.

Could enough New Yorkers have contracted the disease to develop “herd immunity?”

The New York State antibody test found that about 15% of the population was exposed to the virus, far below the level experts agree would be needed for herd immunity. The Johns Hopkins Bloomberg School of Public Health estimates that to achieve herd immunity for COVID-19, at least 70% of the population would have to be immune.

Could those who recovered from COVID-19 help those who are sick?

Researchers at Stony Brook University Hospital are testing whether they can help sick patients by transfusing them with antibody-rich blood plasma from recovered patients.

How does an antibody blood test work?

Some require a finger prick, while others require drawing blood from a vein. Some have results within a few minutes, while others have to be processed in a laboratory.

How accurate are antibody tests?

Many inaccurate tests came onto the market, prompting warnings from Dr. Deborah Birx, chairperson of the White House’s COVID-19 task force. Reliability is expected to improve as major companies enter the market.

Will antibody tests be available to the public?

Antibody tests and separate tests showing whether someone is presently infected are becoming increasingly available as major pharmaceutical companies ramp up production and pharmacies begin administering tests.

Where can I get the test and when?

Start by calling your physician’s office. They may be able to administer the test at the office or direct you to a laboratory.

For instance, Quest Diagnostics, a major testing company with laboratories around Long Island, offers the tests through physicians’ offices or direct purchase at GetQuestTest.com.

Some urgent care centers also are offering the test. Among them are CityMD Urgent Care and the AFC Urgent Care centers in West Islip, Farmingdale and East Meadow.

Some pharmacies also are rolling out antibody testing. Rite-Aid is beginning to offer the tests, but the service has not yet reached Long Island.

The antibody tests, also called serology tests, vary. Some require blood drawn from a vein and some require a finger prick.

The tests are covered by insurance plans and Medicaid.

What questions should I ask?

Ask if the test is covered by insurance, to make sure that the laboratory is following federal guidelines. Ask about the test’s accuracy rate, since that varies among tests.

Sources: Centers for Disease Control and Prevention, National Institutes of Health