- The low residual risk is attributable to the low incidence rate of these diseases in the donor population and the improved sensitivity of the test methods.
- Limitation of the residual risk calculation include the inability to calculate incidence of seroconversion in one time (or first time) donors. These donors represent 20% of blood donations. Also, individuals who remain immunosilent (seronegative) are not included, although this number is estimated to be very small.
- Risk of an infectious unit entering the blood supply is higher if donated from a first time donor compared to a repeat donor.