Medical News

New University of North Carolina Study Reveals Screening Tests Can Boost Early Discovery of AIDS Virus

August 13, 2002

This article is part of The Body PRO's archive. Because it contains information that may no longer be accurate, this article should only be considered a historical document.

Early, widespread diagnosis of acute infection with HIV is not only possible but also feasible -- by pooling blood samples from people being screened for HIV and conducting nucleic acid (polymerase chain reaction) tests on those grouped specimens, a study published in the July 10th issue of Journal of the American Medical Association shows ("Real-time, Universal Screening for Acute HIV Infection in a Routine HIV Counseling and Testing Population," 2002;288:216-221). The more sophisticated testing, now used by the nation's blood banks, would be a distinct improvement over routine antibody tests, which cannot detect the virus for up to two months postinfection, researchers said.

Nucleic acid screening of pooled blood can boost the total number of people diagnosed by about 10 percent, said study head Dr. Christopher D. Pilcher, assistant professor of medicine at University of North Carolina School of Medicine. Increased costs would be minimal -- about $2 dollars per test, or $4,109 for each new case diagnosed -- figures that pale by comparison with the financial and human burden of missing a case or missing the opportunity to prevent further HIV transmission.

"The acute stage of infection is almost never diagnosed in clinical practice and is always missed by routine antibody tests," said Pilcher. "So without this type of testing, we miss the time when we know that people have by far the most virus in their blood and are ... most infectious. If we can catch infected people during the first weeks when routine antibody tests are still negative, we can help them avoid spreading HIV ... ."

Researchers focused on 8,505 people who visited 110 publicly funded testing sites in North Carolina for routine HIV testing and counseling in August and December of 2001. Of the 8,194 subjects who had not previously tested positive for HIV and also had enough serum for additional evaluation, investigators found 39 with long-term HIV infection. Then, using specimen pooling and nucleic acid testing, the team found four additional people -- all women -- with acute HIV infection among the 8,155 people whose antibody tests were negative.

Laboratory workers draw off portions of serum from ten antibody-negative specimens, combining these into a single pool, Pilcher explained. Portions of each of the pools of ten are drawn and combined to make pools of 90. By testing the largest pools and then, if necessary, the smaller ones, laboratory staff can see which pools are negative for HIV and thereby eliminate all individual testing of constituent specimens. If a smaller pool tests positive, each specimen is tested individually by polymerase chain reaction.

"One important thing we proved with this new work was that a significant number of contagious infections are being missed by routine antibody testing," Pilcher said. "The nucleic acid testing, or PCR, detects patients who may represent a public health threat and who would ordinarily get a falsely reassuring 'negative' test result. We hope that this type of testing can help us cut the risk for the unsuspecting partners of acutely infected patients."

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Adapted from:
AIDS Weekly

This article was provided by CDC National Prevention Information Network. It is a part of the publication CDC HIV/Hepatitis/STD/TB Prevention News Update.


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