In this issue of the Revista Brasileira de Hematologia e Hemoterapia, Loureiro et
al. present their evaluation of the use of confidential donation confirmation (CDC),
i.e., release of blood units from donors who have confirmed that their blood may be
used for transfusion by choosing the "yes" option.(1)
The conclusion of this case-control study is that CDC did not reduce the residual
risk of transfusion-transmitted infections (TTIs) nor did it deter at-risk donors
from donation. In brief, no real benefit was associated with the use of CDC.
The safety of the blood supply has been improved over the years by the progressive
implementation of measures aimed at reducing the risk of TTIs. The use of voluntary
nonremunerated donors, the implementation of donor education programs, the careful
selection of donors interviewed before their donation using donor questionnaires and
the development of sensitive laboratory screening assays have all contributed tremendously
to the improvement in blood safety. Over the last decade, the use of nucleic acid
amplification technology (NAT) has improved blood safety by reducing the window period
and the residual risk of human immunodeficiency virus (HIV) transmission around the
world.(2,3) Nowadays, a lower prevalence of infectious diseases is observed among
blood donors and the immunological window periods for these infections have been shortened
remarkably.(3) However, global and regional differences persist due to higher or lower
incidences of diseases and, because of the window period, there will always be a residual
risk for TTIs. The improvement in blood safety therefore requires ongoing effort within
a wide range of contexts.
In 1986, the U.S. FDA recommended the use of confidential unit exclusion (CUE).(4)
This approach allows at-risk donors to confidentially exclude their blood from being
used for transfusion. However, the use of CUE is controversial as many authors have
reported that CUE has low sensitivity, a low positive predictive value(5-7) and no
proven benefit in terms of improving blood safety. Furthermore, CUE has even been
associated with a small but constant loss of apparently safe donations.(7) For this
reason, the CUE is no longer in use in most U.S. blood banks(8) However, CUE is still
used or recommended in other countries, such as in the United Kingdom,(9) Switzerland,(9)
Iran,(10) Brazil(11,12) and Germany.(9)
The use of CUE has been evaluated in countries where NAT screening is performed and
where the residual risk of HIV transfusion-transmission is lower, such as in Germany
and Canada and results have shown that the sensitivity and positive predictive values
of CUE are very low and it has minimal impact on transfusion safety.(9,13) Also, the
researchers concluded that the efficacy and usage rate of CUE depend very much on
the demographic characteristics of donors as well as the design of the CUE form and
procedures.
In Brazil, NAT screening for HIV is not performed routinely by most blood banks. This
results in a longer infectious window period and substantially greater residual risk
of transfusion-associated transmission of HIV than in the U.S.(2,3) and Europe.(14,15)
In Brazil, estimates of HIV incidence are approximately 10-fold higher in first-time
donors than in the U.S.(3) and Europe.(15) A recent study by Dr. Sabino et al.(16)
showed that even with the implementation of NAT, the risk of residual HIV in Brazil
will remain higher than it was in the U.S. prior to NAT screening.(3,17) In this case,
the use of CUE could potentially help exclusion of units donated during the HIV window
period.(18)
The CUE or CDC approaches have been used in several Brazilian blood banks in compliance
with local regulations or recommendation.(12) Mendrone et al.(19) found that, in the
absence of better methods to reduce the HIV window period, the CUE option would potentially
prevent only a few cases of transfusion-transmitted HIV infection. Almeida-Neto et
al.(18) demonstrated that the use of the CUE option, although resulting in a high
number of discarded units, was predictive of marker-positive donation and thus appeared
to contribute modestly to blood safety.
As long as no consensus has been reached on the use of CUE or CDC to prevent high
risk blood donors from donating blood, the rights of the recipients to receive the
safest possible blood supply should prevail. Meanwhile, blood bankers are investigating
ways to improve blood safety for the community and further studies, in each locale,
will be important for informed decision making about CUE, CDC or other measures. In
the interest of recipients, high risk blood donors should be excluded from donating
blood. Thus, the use of CUE might contribute to an improvement in the safety of blood.
CUE might be even more relevant in middle- and low-income countries with high prevalence
and incidence rates of HIV, in countries with high rates of prejudice and stigma against
HIV positive persons, in countries where infections are not concentrated in specific
at-risk populations (i.e., where donor deferral questions are not as efficient) such
as sub-Saharan African countries, or in countries where costly measures to reduce
the risk of TTIs (e.g., NAT testing) are not feasible and where access to alternative
testing is limited. In Brazil, as NAT screening will be implemented in the entire
country in the near future, larger scale studies would be useful to balance the benefit
of using CUE or CDC in addition to NAT screening to reduce the number of units from
risky but test-negative donors with the loss of blood units from safe donors.