A new test to measure the rate of HIV infection in populations is raising hopes among health officials that they’ll be able to figure out more quickly and cheaply which methods work best to prevent the spread of HIV/AIDS.

Known as the Limiting Antigen Avidity Enzyme Immunoassay, the test to measure HIV incidence was developed by the U.S. Centers for Disease Control and Prevention.

It can tell whether a person was infected recently — within the last 141 days — or earlier.

That’s hugely important information for researchers, who need to know whether fewer people are becoming newly infected with HIV to determine whether a prevention program is working.

In a speech at the XIX International AIDS Conference in Washington last month, Secretary of Health and Human Services Kathleen Sebelius called the new test “a major development that will help us better evaluate and improve our prevention efforts.”

Much of the discussion at the conference was about how to expand the use of methods that science has shown significantly prevent or reduce the spread of HIV infection — methods that the U.S. government has so far spent billions of dollars to implement domestically and overseas.

The hope is that using such methods in combination — AIDS drug therapy, male circumcision, and others — can bring down the rate of new infections, helping to curb the epidemic. The new test can help researchers figure out which of those methods and combinations work best. Incidence is the rate of new infections in a population — so it shows how a disease is spreading.

It works by measuring how tightly an antibody against the HIV virus has bound to the HIV protein, says Dr. Bharat Parekh, who heads the lab at the CDC’s Center for Global Health where the test was developed. When a person is initially infected, that binding is weak, but it becomes stronger over time, he tells the Health Blog. The test works on any strain of the HIV virus; strains differ in the U.S. and Africa.

The CDC tried the new test in Swaziland late last year. The agency used both a traditional method of measuring incidence and the new test; the task was to determine HIV incidence in the country ahead of the implementation of a big program to circumcise males to reduce the spread of HIV.

The traditional method, known as a longitudinal cohort estimate, involved analyzing blood samples from 12,000 HIV-negative men and women, and then going back, door-to-door, six months later to resample the same 12,000 to see if any had become infected.

The new lab test analyzed blood samples from 6,000 people who had already tested positive to see how many had been recently infected.

Both tests came up with similar results; the longitudinal study found HIV incidence in the country to be 2.4% while the lab test found 2.6%.

The difference is that the new lab test took 10 days and cost thousands of dollars, while the traditional method involved two rounds of sampling six months apart and cost millions of dollars, says Yen Duong, a microbiologist in the CDC’s global health HIV lab.

“We saved a year that could have been spent on prevention,” she says.

The test is commercially available from Sedia Biosciences and now is being used in countries such as Kenya, South Africa and others where the U.S. President’s Emergency Plan for AIDS Relief operates, Duong says.

“Now we have a tool that actually directly measures our impact,” she says.

The hope is that, in the future, doctors or clinics will be able to use the test to help individual patients learn how recently they were infected.

“What we hear a lot from counselors and testers is that people would like to know when they were infected,” she says. “This assay is accurate enough that we’re looking to develop it for individual use.”