New, faster blood test may make blood supply safer
New, faster blood test may make blood supply safer
Nucleic acid testing under way in 16 labs
The nation’s major blood suppliers are investigating the use of an HIV test that could move the United States closer to a 0% blood infusion transmission rate.
Milwaukee Blood Center in Wisconsin was the first blood center in the nation to identify a positive HIV test using a new technology that can detect HIV infection about two weeks earlier than standard tests. The new test’s purpose is to detect viruses within the window period of when viruses are not detectable through normal testing methods.
Reducing window from 22 days to 10
Using the antibody test, the window period is about 22 days; the p24 antigen test reduces that window period to 16 days; the new test that Milwaukee Blood Center used, called nucleic acid amplification technology (NAT), reduces the window period to about 10 days, says Melissa McMillan, a spokeswoman for America’s Blood Centers in Washington, DC.
NAT, developed by Rouche Molecular Systems in Pleasanton, CA, and Chiron Corp. in Emeryville, CA, identifies HIV genetic material circulating in the blood stream.
Milwaukee Blood Center is a member of America’s Blood Centers, which is a nonprofit network with 73 members that collect about 47% of the nation’s blood supply.
America’s Blood Centers has been testing the use of NAT in 16 laboratories across the country.
"We’re just studying NAT’s effectiveness at this point," McMillan says. "Because NAT has been one of the most complex and sophisticated technologies we’ve used, and so the start-up costs are enormous, we wanted to try it at a few labs and get the bugs out and make it efficient."
The network has invested millions of dollars in the technology, as well as time to study NAT’s effectiveness and safety. The data will be used by the Washington, DC-based Food and Drug Administration when it decides whether to license the test, she adds.
The nation’s blood supplies have become extremely safe since the 1980s, with the current risk of transmitting HIV estimated to be one in 676,000 per unit of blood. "What we traditionally see are one or two cases a year, and sometimes not even that much," McMillan says.
"We want to reduce it to as close to zero as we can, and we’re trying to make it a virtually risk-free supply, so we’re doing everything we can that technology will allow," she explains.
Test developed to screen for hepatitis C
NAT actually was developed to reduce the risk of transmitting hepatitis C through blood transfusions. That risk currently is about one in 100,000-150,000. One reason hepatitis C is more easily transmitted is because the antibody tests have a window of about 70 days. NAT is expected to reduce that window to between 20 and 30 days.
Blood centers will be able to use the same samples to test for both HIV and hepatitis C using NAT, which could raise the cost by $5 to $7 per donation.
"In both cases, by shortening the window period, if you are able to identify an NAT-positive donation that was negative by the standard test, then you prevent these products from entering the blood supply, and the donor who gave the blood will be able to get into a therapy regimen much sooner," McMillan says.
In the case of Milwaukee’s positive NAT test, the donor returned three times so the center could verify the result through antibody and antigen tests. "Over a two-week period, we did a series of confirmation tests to double-check because NAT does have false positives from time to time, and we don’t want to alert somebody unnecessarily," McMillan says.
It’ll probably be another year before NAT is licensed and available for commercial use, McMillan notes.
"This is an entirely new way to screen the blood supply," she says. "This literally has been an exhaustive effort on the part of blood centers and companies we’ve been working with to make this feasible."
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