Effective procedures for virus inactivation are required in the manufacturing of all US licensed plasma derivatives. However, 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, of Los Angeles, California, 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 amplification of a gene fragment.
The approved test systems permit highly sensitive detection of RNA from HCV and HIV-type 1, in test pools of 512 plasma samples obtained from multiple donors.
| HCV can be detected 57 days earlier with the NAT system.
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. The donor can then 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's 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.