Annually, millions of people worldwide receive blood transfusions or blood-derived products. Around the world, more than 112.5 million blood donations are collected every year.
From these, a single whole-blood donation can be transfused in up to three people, while blood-derived products from a single donation may be given to hundreds of patients.
Although testing and policy decisions have combined to make blood supplies in many countries among the safest in the world, there still exists some risk of transfusion-transmitted infection (TTI) with bloodborne diseases (e.g., HIV, hepatitis, or West Nile virus [WNV]). Laboratory screening of donated blood and blood products for infectious diseases is a key safety measure in protecting patients and preventing the spread of serious diseases.
Significance of Blood Screening
Compared to 30 years ago, TTI risk in countries worldwide has decreased substantially. Active screening and hemovigilance programs are credited with having impacted the rate of TTIs. Nucleic-acid testing (NAT) has also played an important role as the most advanced technology for directly detecting infections in blood. Today, NAT has been adopted in countries around the world, including in the U.S., Canada, France, Australia, New Zealand, South Africa, and many countries in Europe and Asia.
The World Health Organization states that “screening for TTIs to exclude blood donations at risk of transmitting infection from donors to recipients is a critical part of the process of ensuring that transfusions are as safe as possible.” As NAT becomes a part of countries' blood-screening protocols, they will likely experience a significant TTI reduction and help ensure that their blood supplies meet international safety standards.
The Value of NAT
NAT detects the presence of viral infection by directly testing for viral nucleic acids and can be used to screen whole blood and plasma samples. Commonly used NAT assays detect HIV-1 RNA, HCV RNA, HBV DNA, and WNV RNA.
Countries that have not yet adopted NAT may use the traditional method for screening blood donations, known as immunoassay (or serology) testing. Immunoassays detect antibodies to viruses or viral antigens. With immunoassays, however, there is an interval between the donor's exposure to a virus until antibodies against the virus are produced, known as the detection “window period.” It is during this period that the risk of infection in donated blood can be missed.
NAT shortens this window period, thereby offering blood centers a much higher sensitivity for detecting viral infections. For example, with serology tests, it takes about two months after infection for anti-HCV antibodies to be detected, while NAT testing can detect HCV RNA in about five days after infection.
Common NAT platforms — fully integrated and automated, semi-automated, and modular automated types — are used with assays to conduct NAT screening in two ways: individual donor testing (IDT) and pooled testing. IDT is done on a sample from each unit of donated blood with no dilution of viral genetic materials required before testing. IDT is the most sensitive method for NAT testing. The viral titers during window periods are often low, and IDT maintains a high level of sensitivity. Pooled testing, in which samples from multiple donors are combined before testing, is preferred by many blood centers that need to process large volumes of blood.
The Future of Global NAT Adoption
NAT technology has revolutionized the ability of blood centers to efficiently test for and intercept potentially infectious pathogens while continuing to ensure on-time blood availability for patients and hospitals. The global trend towards adopting this technology helps underscore its effectiveness for increasing the safety of blood supplies. As reducing the rate of transfusion-transmitted disease gains speed in more countries, NAT can serve as a valuable addition to existing safety efforts.
Sansure Biotech Inc. helped to create NAT blood screening platform these years, please visit http://eng.sansure.com.cn/index.php?g=portal&m=article&a=index&id=78 for more information.