New test catches more HIV cases

Nucleic acid testing (NAT) for HIV identifies 23 percent more patients with the virus compared to a standard antibody test, researchers say.

Their study also found that offering results electronically may increase the number of people who get tested.

NAT also reduces the average window period – when patients may be infected but test negative for the virus – for identifying HIV to 12 days after infection, compared to 22 days for an antibody test and 16 days for an antigen test.

“HIV nucleic acid testing is useful in certain scenarios and doctors do order the test, [for example,] in babies born to mothers who are HIV positive, in very early infection before the antigen or antibody is detectable, or in clinical management of an infected person by measuring the viral load,” said Dr. Chan Kwai Peng, a senior consultant in the Department of Pathology at Singapore General Hospital, who was not involved in the study.

However, the NAT is more expensive than rapid antigen or antibody blood tests, and Chan said antigen and antibody tests work well in most cases.

But since people are most infectious in the acute phase, identifying HIV infected individuals sooner may help prevent transmission.

In the prospective study, researchers from the University of California, San Diego, gathered data from 3,151 people tested at community-based centers around San Diego County, California, US. [Ann Intern Med. 2010 Jun 15;152(12):778-85]

Seventy nine people were newly diagnosed with HIV, of which 64 had positive results after a rapid antigen HIV test and 15 had positive results only after NAT – a 23 percent increase in detection yield. Thirty five (44 percent) of the total HIV infected persons were identified in the acute and early stages.

The researchers also determined that persons with higher incomes, younger age, no recent syphilis, no methamphetamine use, those not associated with substance abuse centers and men reporting sex with men were more likely to access their test results online or via a phone message, if offered.

Of the 3,070 uninfected patients, 2,105 (69 percent) retrieved their results without returning to a clinic and 1,358 of those used an internet system.

“Findings may not be generalizable to other populations and testing programs, [but] nucleic acid testing programs that include automated systems for result reporting can increase case yield,” the researchers said.

They also noted that only negative results would be available without having to return to a clinic. Positive results still required a phone call and in-person visit.

But some remain wary of digitizing sensitive test results for individual access, whether they are positive or negative.

“Using such means, there is always the risk that the confidential result may end up with someone who has no business to possess such knowledge, potentially leading to problems, even if the result is negative,” Chan said. “Further, whether the result is positive or negative, the patient needs counseling and this is best done when the results are given at a face-to-face encounter.”

Source: mims.com