The Food and Drug Administration has licensed the first nucleic acid test (NAT) systems intended for screening of plasma donors. These test systems are expected to further ensure the safety of plasma-derived products by permitting earlier detection of HIV and HCV infections in donors.
Although effective procedures for virus inactivation are required in the manufacturing of all U.S. licensed plasma derivatives, removal of potentially infectious donations through donor screening adds a safeguard by limiting the amount of virus contamination that the manufacturing process must clear.
The newly approved test systems were developed by National Genetics Institute (NGI) for screening plasma used in manufacturing of products such as clotting factors and immune globulins. Alpha Therapeutic Corporation was also approved to use new testing systems at its plasma collection facilities.
NAT is a recently developed technology that allows detection of very small amounts of genetic material (DNA or RNA) by a process of massive copying (amplification) of a gene fragment.The approved test systems permit highly sensitive detection of RNA from HIV, type 1 (the HIV variant that is responsible for the vast majority of AIDS cases in the United States) and HCV in test pools of 512 plasma samples obtained from multiple donors.
The use of pooled plasma samples for testing makes use of the NAT system cost-effective. However, if a test pool is positive for either virus, the individual donation that is suspected of containing a virus can be identified and not used for further manufacturing, and the donor can be deferred and notified.
Currently, donors of blood and plasma are tested for antibodies to HCV, antibodies to HIV, and HIV-1 antigens, which are the virus' own proteins. However, there is still a "window period" during which a donor can be infected, but have negative screening tests. With the use of NAT for HCV, the "window period" for detection of HCV is reduced by 57 days (from an average of 82 days to 25 days). For HIV-1, the average window period with antibody tests is 22 days. Antigen testing cuts the window period to approximately 16 days and NAT further reduces this period to 12 days.
In the clinical trials that supported these approvals, a total of 342,729 donations from approximately 48,000 donors collected at 33 plasmapheresis centers were tested for HIV-1 and HCV. The NAT systems detected a number of HIV and HCV infections that would have been missed by previously licensed test methods, confirming the effectiveness of these systems. Additionally, use of the NAT system for HIV will allow Alpha Therapeutic Corporation to discontinue antigen testing, although antibody testing will still be done on all plasma donations.
Since 1997, FDA has encouraged the investigation of NAT technology through the use of experimental protocols, in the hope of improving the safety of plasma derivatives and further reducing the risk of an infectious unit of blood being transfused.
National Genetics Institute is located in Los Angeles, California. Alpha Therapeutic Corporation is also located in Los Angeles.