Effectiveness of confidential unit exclusion for screening blood donors

The confidential unit exclusion (CUE) option in the process to screen blood donors was conceived in the 1980s as a possible means to reduce the risk of transfusion transmission of HIV before sensitive tests became available. The use of CUE allows blood donors at increased risk for HIV or other sexually-transmitted diseases who may feel pressured to complete the donation, or who are inappropriately donating blood in order to be tested, a chance to confidentially indicate that their blood should not be used for allogeneic transfusion. CUE has been abandoned by blood centers in many countries but is still voluntarily used or mandated in other jurisdictions. The centers that have eliminated CUE largely based their decisions on published evidence that the process did not improve safety and was more often misunderstood and incorrectly used by donors, leading to the unnecessary waste of many safe donations. The effectiveness of CUE, however, could still differ among blood centers because of the various methods to administer the CUE option, variability in the criteria to select blood donors, the performance characteristics of laboratory tests, or disparate demographics among donor populations. Consequently, blood centers that continue to use CUE, either as a voluntary or compulsory measure, should evaluate its effectiveness in their donor population. To that end, Volger and colleagues report on the effectiveness of CUE in the screening of blood donors of a regional blood bank of Londrina, Parana State. The authors evaluated the donors' use of CUE in 51,104 successful donations during the period of January 2004 to December 2008. Their CUE instrument consists of 4 questions related to intravenous drug use, sexual activity with a partner of the same gender, "professional of sex" and occasional sexual partner. The frequency of positive serology was 5.3% in the group that used CUE and 3.5% in the group that did not use CUE (χ 2 =15.66; p-value < 0.0001). Eighty-nine of 1672 donors who used the CUE option had at least one reactive serological test result. Follow-up testing for 8 donors who had reactive serological tests after a positive CUE donation failed to identify seroconversion after self-exclusion: 4 of the 8 were falsely-reactive for T cruzi antibodies (2 donors) or anti-HCV (2 donors) and were readmitted for future donations, one had inconclusive results for Chagas' disease, two were reactive for VDRL and one failed to return to be tested for HIV1/2. The results are consistent …