Dr D. Scott, USA

The ability of plasma derivatives - such as coagulation factors and intravenous immunoglobulins-to transmit viral infections is well documented. To prevent such occurrences, adequate safety measures must be in place for donor screening and testing, plasma processing, and at the end-user level.

Donor screening, for risk factors and medical history, identifies those who may be deferred for risk of viral infection. Survey results suggest that donor testing inaccuracies occur in approximately 1.8% of US blood donors, indicating that screening questions alone may not always effectively defer donors with viral infections.

Viral testing of donated blood components is now a required standard for HIV and hepatitis viruses (B and C). The US-approved conventional tests include antigen and antibody detection. Nucleic acid testing (NAT) for HCV and HIV may become the industry standard. However, HIV and hepatitis transmissions in the 1980s, and HCV transmission by IGIV in the 1990s, demonstrate that intentional viral clearance steps are essential in plasma derivative manufacture. Well-validated methods for inactivation of enveloped viruses, such as HIV and HCV, include heat treatment and solvent/detergent treatment.

Effective viral clearance for a product should be demonstrated by scaled-down experiments which mimic fractionation steps, using appropriate viruses or surrogate viruses. Finally, post-marketing surveillance for possible viral transmissions by plasma-derived medicinals, and a mechanism for rapid, effective product withdrawal if this event were to occur, should be implemented.