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- The residual risk is defined as the risk of acquiring a
transfusion transmitted infection from a donation of blood by a donor who tests negative
for all of the routine infectious disease tests. In other words, the residual risk is the
probability that a seroconverting donor gave an infectious unit of blood during the window
period that was not detected as seropositive by the screening tests currently used and
therefore could have been given in transfusion. These individuals represent new or
incident infections.
- Incidence is calculated as the number of confirmed seroconverting donors divided by the
total number of person-years at risk. A seroconverting donors is defined as a donor who,
during the study period, initially made a serologically negative donation followed by a
serologically positive donation. The total number of person years was calculated by
totaling the intervals between donations for all donors. For seroconverting donors, an
adjustment was made by assuming that the seroconversion occurred midpoint between
donations. |
