The safety of the donated blood supply results from a system designed to protect both the donor and the recipient. Donated blood is subjected to rigorous laboratory analysis for infectious diseases, including those that are sexually transmitted. In the United States, the Food and Drug Administration (FDA) oversees and mandates these safety standards for blood collection and testing. This process involves multiple safeguards, beginning with donor screening and extending through advanced laboratory testing before any unit is deemed safe for transfusion.
The Mandatory Infectious Disease Screening Process
Once blood is collected, a sample is sent to a specialized laboratory for mandatory screening for infectious agents. This comprehensive testing includes viruses like Human Immunodeficiency Virus (HIV) types 1 and 2, Hepatitis B and C, and the bacterium that causes Syphilis, Treponema pallidum. The blood unit is quarantined and is not released for patient use until all test results are non-reactive.
Modern blood screening relies on advanced molecular technology, such as Nucleic Acid Testing (NAT). NAT detects the genetic material (RNA or DNA) of the virus itself, allowing for detection much earlier than traditional tests that look for antibodies or antigens. This method enhances safety by closing the window of time during which an infection might be present but undetectable. The blood supply is also tested for other agents like Human T-lymphotropic Virus (HTLV) types I and II and, in certain regions, West Nile Virus or Trypanosoma cruzi, the parasite that causes Chagas disease.
Donor Eligibility and Pre-Donation Screening
Before donation, all prospective donors must complete a confidential health history questionnaire and participate in a private interview with a trained staff member. This pre-donation screening evaluates a donor’s current health status and recent risk behaviors associated with carrying an infectious agent.
The questions focus on lifestyle and medical history, assessing factors that increase the likelihood of harboring a transfusion-transmissible infection. An individual may be temporarily or permanently deferred from donating if their answers indicate a higher risk, even if they feel healthy. This behavioral screening complements laboratory testing by filtering out high-risk donations before testing is incurred.
Understanding the Residual Risk
Despite the rigorous layering of donor screening and laboratory testing, a residual risk remains. This risk is primarily due to the biological limitation called the “window period,” which is the time between initial infection and when the virus level is high enough to be detected by screening tests.
Even with highly sensitive NAT technology, which has dramatically reduced this window period, a donation made during this early phase of infection could still test negative. However, the residual risk of transmitting major viruses like HIV, Hepatitis C, and Hepatitis B is exceptionally low, estimated to be less than one in a million donations for each virus in the United States.
Donor Notification and Confidentiality
If a blood unit tests reactive during infectious disease screening, it is immediately removed from inventory and discarded. The blood collection center is required to confidentially notify the donor of the positive result. This process is handled with strict confidentiality, protecting the donor’s personal health information.
The primary goal of notification is to inform the donor of a potential health concern and recommend medical consultation and follow-up care. A donor who tests positive for a transfusion-transmissible infection is also placed on a permanent deferral list, preventing future donations. This measure protects the recipient supply and fulfills the center’s obligation to inform the donor about their health status.