The test may be useful for screening donated blood and monitoring patients, the developers at the University of Maryland’s Institute of Human Virology said.

They said it is 25 times more sensitive than the best technology currently available. "This new ultra-sensitive testing method, known as Real-Time Immuno-PCR, will allow us to detect HIV earlier and at much lower levels," said Dr. Niel Constantine, who helped develop the test.

Writing in the July issue of the American Journal of Clinical Pathology, Dr. Constantine’s team said the new test detects the viral protein p24, rather than antibodies or viral nucleic acids.

"Each virus particle contains about 3,000 molecules of p24 as compared with only two copies of nucleic acid, so there’s a greater amount of target to detect," Dr. Constantine said.

"It’s an advance over current methods in that we can detect down to the equivalent of two copies of RNA as compared with current methods which have been validated to only 50 copies," his colleague, Janet Barletta, added in a statement.

"We have submitted a patent for this test for the prion protein," Dr. Constantine added in a telephone interview. He believes it could be used to screen blood for Creutzfeldt Jakob disease or HIV.

"If you could save 4 to 5 infected units a year, it would be important to do that," Dr. Constantine said. "You could further protect the blood supply."

It should also be useful for monitoring a patient’s response to HIV treatment.

The research team is also developing a low-cost, battery-operated version of the test that could be used in developing countries.