STI Screening for Plasma Donation
All plasma donors must be screened for Hepatitis B (HBsAg), Hepatitis C (anti-HCV), HIV, and syphilis, with any repeatedly reactive result causing indefinite deferral from transfusion donation. 1
Required Screening Tests
Plasma donation facilities must test all donors for the following transfusion-transmissible infections:
- Hepatitis B Surface Antigen (HBsAg) - detects active HBV infection
- Anti-HCV antibodies - screens for Hepatitis C virus exposure
- HIV antibodies (anti-HIV-1 and anti-HIV-2) and p24 antigen
- Syphilis - typically using treponemal or non-treponemal assays
Modern blood banking also employs nucleic acid testing (NAT) for HIV and HCV to detect infections during the window period before antibodies develop 2, 3.
Infections Causing Donor Deferral
Indefinite Deferral from Transfusion Products
Hepatitis B: Any donor testing positive for HBsAg must be indefinitely deferred and cannot donate blood, plasma for transfusion, organs, tissues, or semen 1. These individuals are chronic HBV carriers capable of transmitting infection.
Hepatitis C: Donors with repeatedly reactive anti-HCV results are indefinitely deferred from transfusion donation 1. However, the FDA currently permits plasma from these donors to be used for fractionation into manufactured products like immune globulins, as the manufacturing process includes viral inactivation steps 1, 4.
HIV and Syphilis: Confirmed positive results result in permanent deferral from all donation types 3, 5.
Critical Testing Algorithm
Initial Screening
All donations undergo enzyme immunoassay (EIA) or similar screening tests. A single reactive result triggers duplicate repeat testing on the same specimen 1.
Repeat Testing Protocol
- If both duplicate tests are non-reactive: donation is acceptable, donor may return
- If either or both duplicates are reactive: result is "repeatedly reactive"
- Unit must be discarded for transfusion use
- Donor receives indefinite deferral from transfusion donation
- Supplemental/confirmatory testing should be performed when available 1
Important Caveats
False Positive Rates: In low-prevalence populations like blood donors, many repeatedly reactive screening results are false positives 6. The anti-HCV repeat reactivity rate among U.S. blood donors is 0.5%-1.4%, but many are not confirmed infections 1.
Plasma for Fractionation Exception: Unlike whole blood or components for direct transfusion, plasma intended for fractionation into manufactured products (immunoglobulins, clotting factors) may currently be accepted from anti-HCV repeatedly reactive donors because manufacturing processes include viral inactivation 1, 4. This does NOT apply to HBsAg-positive donors.
Window Period Risk: Even with sensitive testing, a small residual risk exists during the window period between infection and test detectability. NAT testing has substantially shortened this window for HIV and HCV 2, 3.
Donor Notification: Repeatedly reactive donors must be notified in writing and informed that results may represent false positives, particularly for anti-HCV without confirmatory testing. They should be referred to physicians for clinical evaluation including liver function tests (ALT, AST) and assessment for chronic infection 1.