Korean J Anesthesiol 2012 May 62(5): 412-417
Clinical Research Article
Background: In this retrospective study, we measured the frequency of unexpected antibodies in the blood. Specific
considerations for preoperative preparations were kept in mind for the patients undergoing surgery positive for these
Methods: After reviewing the results of antibody screening tests lasted for 2 years, the frequency of unexpected
antibodies was determined. Surgical patients who were positive for unexpected antibodies were selected and
divided into two groups based on their potential need for an intra-operative transfusion (groups with high versus low
possibility of transfusion). Blood for the high possibility group was prepared before surgery. For the low possibility
group for which preoperative blood preparation was not performed, cases of this group were reviewed whether a
blood preparation was delayed or not in case of transfusion.
Results: Among a total 22,463 cases, 340 (1.52%) had positive results for antibody screening tests. Among the 243
patients who were positive for unexpected antibodies, Lewis, Rh, Xga, and mixed antibodies were found in 85, 25,
five, and eight cases, respectively. Out of 243 patients, 117 patients, specificities of the unexpected antibodies were
not determined and 125 (51.4%) had a history of pregnancy and delivery, and 49 (20.2%) had a history of transfusion.
In the low probability group, transfusions were administered for nine patients; transfusion was delayed for two
patients due to difficulties with obtaining matched blood.
Conclusions: Patients with unexpected blood antibodies may be at increased risk for delayed transfusion. For rapid
transfusion, it might be helpful to keep a record about blood antibodies and introduce a notification system such
as medical alert cards. Preoperative blood preparation is needed for timely intraoperative transfusion. (Korean J
Anesthesiol 2012; 62: 412-417)
Key Words: Antibodies, Blood transfusion, Complications.
Frequency of unexpected antibody and consideration
Ki-Ho Ko1, Byung-Hoon Yoo1, Kye-Min Kim1, Woo-Yong Lee1, Jun-Heum Yon1, Ki-Hyuk Hong1, and
Departments of 1Anesthesiology and Pain Medicine, 2Laboratory Medicine, Sanggye Paik Hospital, College of Medicine,
Inje University, Seoul, Korea
Received: July 11, 2011. Revised: September 6, 2011. Accepted: September 9, 2011.
Corresponding author: Byung-Hoon Yoo, M.D., Ph.D., Department of Anesthesiology and Pain Medicine, Sanggye Paik Hospital, College of Medicine,
Inje University, 761-1, Sanggye 7-dong, Nowon-gu, Seoul 139-707, Korea. Tel: 82-2-950-1173, Fax: 82-2-950-1323, E-mail: email@example.com
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://
creativecommons.org/licenses/by-nc/3.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium,
provided the original work is properly cited.
Copyright ⓒ the Korean Society of Anesthesiologists, 2012
Korean J Anesthesiol
Ko, et al.
One of the most important issues for patient care during
anesthesia is managing bleeding. For this, it is important
to know the patient’s pre-operative hemoglobin levels and
coagulation function, as well as the status of important
organs. Based on this information, the appropriate amounts
of fluids and blood to be administered during surgery can be
determined. When managing bleeding, the first concern is to
reduce the amount of bleeding during surgery while the second
concern is to mitigate complications associated with transfusion
. For the latter, it is important to be aware of the existence and
specific characteristics of unexpected antibodies identified in
Unexpected antibodies are sometimes referred to as irregular
antibodies because their existence and type are unknown
before conducting a antibody screening test. This category
of antibodies includes most blood type antibodies excluding
ABO and some P blood type antibodies . Depending on
the type of antibody, some develop naturally in patients but
most unexpected antibodies are formed as part of the immune
response after exposure to foreign antigens during pregnancy
or transfusion. These antibodies can cause acute and delayed
hemolytic transfusion reactions; there are many reports of such
cases [3,4]. It is therefore important to conduct test to screen for
and identify unexpected antibodies before transfusion.
For patients who require transfusions, it is vital to conduct
pre-operative testing to minimize complications and improve
transfusion safety. For these reasons, it is essential to know
the frequency and distribution of unexpected antibodies
among South Koreans for prompt and safe transfusion .
The purpose of this study was to examine the frequency and
type of unexpected antibodies found by antibody screenings
conducted in our hospital from 2009 to 2010. In addition, we
examined problems and issues associated with transfusion
when unanticipated bleeding occurs in patients who are
positive for unexpected antibodies.
Materials and Methods
In Sanggye Paik hospital, 22,436 tests to screen for un-
expected antibodies were conducted from 2009 to 2010. Data
were examined to calculate the frequency of unexpected
antibodies. The unexpected antibody test results for 243
surgical patients who were positive in the screening were then
examined. Information about the gender, pregnancy history,
parity, and transfusion history of these patients was collected
from the electronic medical records of the hospital. The 243
surgical patients who were positive for unexpected antibodies
were divided into a high possibility group and a low possibility
group for transfusion based on the likelihood of 500 ml of
predicted blood loss. Additionally, the availability of matched
blood before surgery and whether an actual transfusion
occurred were determined.
Unexpected antibody screening test
A quantitative test was performed using the Ortho BioVue
microcolumn agglutination system (Ortho-Clinical Diagnostics,
Raritan, NJ, USA). The test was performed according to the
Unexpected antibody identification test
When the screening test results were positive, an unexpected
antibody identification test was performed with a microcolumn
agglutination system using ID-Diapanel I, II (DiaMed, Murten,
Switzerland) and LISS/Coombs cards (DiaMed).
Frequency of unexpected antibodies
Among a total of 22,436 cases for which unexpected antibody
screening tests were conducted, 340 (1.52%) were positive. The
number of positive patients according to year was 116 (1.13%)
for 2009 and 127 (1.04%) for 2010. The proportions of positive
screening results were similar despite an increase in the
number of subjects (Table 1). Among the patients positive for
un expected antibodies, 243 were patients underwent surgery.
The gender, parity history, and transfusion history of these
individuals are shown in Table 2.
Table 1. Frequency of Unexpected Antibodies
No. of patient with
No. of patients with unexpected
antibodies undergoing surgery
Data are expressed as the number (percentage).
Vol. 62, No. 5, May 2012
Unexpected blood antibody
Type and distribution of unexpected antibodies
The results of the unexpected antibody identification tests
conducted for the 243 surgical patients showed that the Lewis
antibody had the highest frequency (30.44%) followed by anti-
Le antibody (21.81%). The frequencies of Rh antibodies were
7.41% for anti-E, 2.47% for anti-D, and 0.41% for anti-C. Two
or more antibodies were found together in 3.29% of cases; one
person had only autoantibodies while another individual had
both autoantibodies and alloantibodies. Unexpected antibodies
were not accurately identified in 48.14% of the cases (Table 3).
Availability of matched blood and actual performance
of transfusion according to predicted blood loss
Out of the 243 surgical patients who were positive for
unexpected antibodies, 43 (17.7%) were in the high possibility
group and 200 (82.3%) were in the low possibility group. In the
high possibility group, there were no cases for which matched
blood was not prepared before surgery. Matched blood was not
prepared for the low possibility group before surgery; situations
that required transfusion occurred for nine patients in this
group (Table 4). For seven cases, there were no difficulties with
securing matched blood, but difficulties in securing matched
blood were encountered for the other two cases. One of these
cases was a patient with no underlying diseases other than
anemia with an Hb of 8.0 g/dl before surgery that decreased to
7.0 g/dl during surgery. Matched blood could not be obtained
for this individual, so surgery continued with the patient
receiving only fluid therapy. Since there was no continuous
blood loss, surgery was completed without transfusion. After
the completion of surgery, an Hb of 7.0 g/dl was maintained,
and there were no major changes in vital signs and no specific
The other patient did not have any underlying diseases, but
had received a transfusion of 11 units of packed red blood cells
during an abdominal operation approximately 2 months prior
to our study. At the time of transfusion, the antibody screening
test results were negative. The patient underwent abdominal
surgery to treat an enterocutaneus fistula, and the operation
protocol included Whipple’s procedure. During the procedure,
excessive bleeding occurred and packed red blood cells were
ordered. However, the blood bank reported that matched blood
was not available. As a result, the patient’s Hb decreased to 4.7
g/dl, and total blood loss reached 3,000 ml. After 3 hours and
30 minutes, 8 units of packed red blood cells that showed the
weakest cross-matching reaction were obtained. Five of these
units were transfused while the patient was carefully monitored
for any transfusion-related complications. The procedure was
completed without any problems and no specific complications
developed after surgery.
The two cases mentioned above involved patients who received
transfusions and were negative for unexpected antibodies. For
both individuals, difficulties in securing matched blood during
Table 2. Characteristics of 243 Patients with Unexpected Antibodies
who Underwent Surgery
History of pregnancy and delivery
History of transfusion
Table 3. Classification of Detected Unexpected Antibodies in 243
Patient who Underwent Surgery
Anti-Le a + Le b
Anti Le a + ?*
Anti E + ?*
Combined with an autoantibody
Autoantibody and non-specific antibody
Unidentified (all positive)
*unable to identify antibody.
Table 4. Number of Patients Who Received Intraoperative Transfusions
High probability of
Low probability of
No. of patients
Data are expressed as the number of patients or percentage.
Korean J Anesthesiol
Ko, et al.
surgery were encountered. Thus, transfusion was delayed.
Through additional screening performed after surgery, both
patients were identified as positive for unexpected antibody.
One was found to have both autoantibodies and alloantibodies
while the other had only autoantibodies.
It is generally known that there are large differences in the
frequency and type of unexpected antibodies found during
screening according to the research subjects, blood type,
genotypic frequency, screening method, and ability of the
decoder . The frequency of unexpected antibodies is reported
to be 1.35% in Denmark , 0.78% in Germany , and 0.3-2%
in the USA [8,9]. In South Korea, the frequency of unexpected
antibodies was reported to be 1.57% by Lee et al. , 0.51% by
Park et al. , and 0.58% by Han et al. . Without considering
differences in research subjects, the mean frequency of positive
results obtained for South Koreans based on the above research
results is approximately 0.84%. The high frequency reported by
Lee et al. is thought to be related to the fact that approximately
96% of the research subjects in this study had undergone
pregnancy and transfusion. The patients in our study also
showed a high frequency of 1.52%, which is thought to be due
to their high rates of pregnancy, parity of the research subjects,
and improvement in screening techniques.
If positive antibody screening results are obtained before
transfusion, an antibody identification test is conducted to
determine the antibody specificity. If the specificity of the
antibody is identified, then the percentage of available blood
that is negative for the relevant antibody is calculated. For
example, if anti-E is found, it can be estimated that 1 out of 2
units of blood in South Korea will be negative for the antibody.
If anti-e antibody is present, it can be estimated that 1 out of
10 units of blood will be negative for the antibody. If 3 units
of blood are to be transfused, 6 or more units of ABO- and
Rh-appropriate blood should be prepared for anti-E-positive
patients, while 30 or more units of ABO- and Rh-appropriate
blood should be prepared for anti-e-positive patients. Then,
blood that is negative for the relevant antibody must be found
by testing with commercialized antibody reagents. The negative
blood is then cross-matched with the patient’s serum, and if it
is observed to be suitable, the blood is secured for transfusion
. Therefore, when excessive blood loss is anticipated during
surgery, matched blood must be obtained before the operation
for prompt and safe transfusion. For cases in which finding
matched blood is difficult, such as ones involving individuals
with anti-e antibodies, the amount of blood loss during surgery
should be predicted for the preparation process.
Alloimmunization responses to red blood cell antigens occur
when unexpected antibodies develop after exposure to red
blood cell antigens that are foreign to the patient . This can
occur due to transfusion or pregnancy. Additionally, antibody
formation can occur due to an anamnestic response when
there is repeated exposure to the same red blood cell antigen.
Antibodies are not formed weeks or even months after initial
exposure to foreign red blood cell antigens. Depending on the
repeated exposure to the antigen, antibodies can rapidly appear
within 48-72 hours after transfusion and reach a maximum
7-10 days later [5,13]. Among the types of alloimmunization
responses, a hemolytic response to the newly formed antibody
is classified as a delayed hemolytic reaction while an absence of
hemolysis is classified as a delayed serologic reaction.
According to existing international report, the rate of detection
of unexpected antibodies after transfusion in healthy people is
approximately 1-1.6% . Retrospective analysis of reports
from Korea medical institutions showed that the detection rate
of unexpected antibodies is about 0.46-1.5% [10,12,14-19]. Park
et al.  determined that the rate of unexpected antibodies
after transfusion was 0.89%. 0.81% of unexpected antibody-
negative patients became positive for these antibodies following
transfusion while 3.38% of unexpected antibody-positive
patients were found to develop more of these antibodies after
The Lewis antibody, which was the most frequently identified
antibody in our study, is an IgM antibody which cannot pass
through the placenta and so is unrelated to hemolytic disorders
in newborns. This antibody, which is detected through direct
agglutination, can occasionally cause hemolytic complications
associated with transfusion and is frequently found in expectant
mothers with no great clinical significance . However, Han
et al.  determined that anti-Le a, which is a type of Lewis
antibody, causes delayed hemolytic reactions. The facts that
Anti-Le a antibodies are mostly formed not from immune
response but spontaneously, and that the patient in their case
had no history of pregnancy or transfusion were cited as the
reasons for their conclusion.
Anti-K, which is has been found at high frequencies in
countries other than South Korea, is a significant alloantibody
which can cause hemolytic disease of newborns or serious
transfusion complications . Formation of this antibody
is mainly due to transfusion or pregnancy, and although its
frequency is reported to be low among South Koreans  and it
was not identified in our study. The reason for this finding is that
despite the consistency red blood cell antigen immunogenicity,
the antigen cultivation rate can vary significantly according
to ethnicity. For example, 9.0% of Caucasians are positive for
K antigen, while only 0.5% of South Koreans are positive for
this antigen; thus, the formation of anti-K antibody following
transfusion or pregnancy in South Koreans is relatively rare .
Vol. 62, No. 5, May 2012
Unexpected blood antibody
Unexpected antibodies that exist at low titers may not be
detected by pre-transfusion tests, but may cause unexpected
hemolytic responses due to the transfusion of red blood cells
that react with the antibodies. In addition, antibody titers can
increase due to secondary immune responses, which can
cause serious hemolytic transfusion complications during a
subsequent transfusion. To reduce the occurrence of delayed
hemolytic reactions, blood samples should be collected
and tested every 72 hours for patients who need multiple
transfusions, or a highly sensitive testing method should be
used for the pre-transfusion test .
The decision of administer transfusions to patients with
autoimmune hemolytic anemia are made according to the
patient’s response to hemolysis, the cause of immunohemolytic
anemia, and the type of antibodies that lead to this condition.
Patients with no history of pregnancy or transfusion are
unlikely to have alloantibodies other than autoantibodies,
and so suitable blood for transfusion can be selected without
conducting an autoantibody absorption test (ZZAP test).
However, judging from the discovery of alloantibodies in 209 out
of 647 patients (32.30%) with autoimmune hemolytic anemia
, the co-existence of alloantibodies should be kept in mind
when selecting matched blood for patients who have received
multiple transfusions or females who have given birth more
than once . In our study, a ZZAP test  was performed on
two patients who had a history of transfusion and were positive
for unexpected antibodies. This confirmed the co-existence
of alloantibodies and autoantibodies. Only autoantibodies
were identified in one of the patients while the other had both
alloantibodies and autoantibodies.
It is difficult to differentiate autoantibodies from alloanti-
bodies because most red blood cells and autoantibodies react.
The effort to find matched blood is necessary when alloanti-
bodies and autoantibodies co-exist, but there is almost no
need to find matched blood when only autoantibodies exist
. Hence, most blood banks transfuse red blood cells that
show the lowest degree of response in cross-matching tests
for patients with only autoantibodies. For individuals with
both auto- and alloantibodies, red blood cells negative for the
relevant antigen that show the smallest response are transfused.
In the latter case, it can be difficult to promptly find matched
blood, so the anesthesiologist must identify the existence of
unexpected antibodies before surgery, and ensure prompt and
safe transfusion through close cooperation with the surgeon
and blood bank.
The main purposes of transfusion are to enhance oxygen
trans portation, maintain appropriate blood volume, and pro-
vide coagulation factors. Among these factors, enhancement
of oxygen transportation is the most important. Timing the
administration of homologous blood is usually determined
based on hemoglobin or hematocrit levels. Factors involved in
this judgment include the patient’s cardiovascular state, age,
anticipated additional blood loss, arterial blood oxygenation,
PO₂ in mixed venous blood, cardiac output, and total blood
volume . Healthy adults do not require transfusion until
Hb decreases to 6 g/dl, but patients with underlying conditions
such as coronary or chronic lung diseases need transfusions
even when Hb is as high as 10 g/dl .
The two patients in our study whose transfusions were
delayed were healthy individuals with no specific underlying
diseases. However, transfusions were ordered because their
clinical status indicated the need for transfusion. Difficulties
with securing matched blood based on cross-matching
were encountered. As a result, one of the patients received a
trans fusion of packed red blood cells that showed the least
cross-matching response. This individual recovered without
developing transfusion-associated complications or other
effects. Although transfusion was delayed in both of these
patients due to difficulties in securing matched blood, no
specific complications developed because the patients were
young and had no underlying diseases. However, patients
with ischemic heart conditions such as coronary, lung,
or cerebrovascular diseases are highly likely to develop
complications due to delays in transfusion.
For patients positive for unexpected antibodies, blood
that does not have antigens which can cause an anamnestic
response should be selected and transfused . Some
medical institutions issue medical alert cards containing
this information for patients to present when hospitalized or
undergoing transfusion . Clinically significant alloantibodies
already formed in the blood can cause hemolytic reactions
during transfusions or pregnancies, so caution is necessary.
Therefore, medical institutions should maintain permanent
records of patients who produced unexpected antibodies
due to an alloimmunization response to ensure safe and
prompt transfusion. Issuing medical alert cards containing
this information, which can be presented at other medical
institutions, should also be introduced.
Fortunately, antibody formation due to anamnestic responses
generally causes only delayed serologic reactions [5,13]. In
some patients, however, high antibody titers and large red blood
cell transfusion volumes can induce hemolytic reactions. The
reported frequency of hemolysis is one case in 5,000-11,000
transfusions, which represents 0.05-0.07% of patients who
receive transfusions . Therefore, when there is a sudden
need for transfusion due to acute bleeding during surgery, the
anesthesiologist should consider the possibility of complications
and risks from transfusion delays. This is particularly important
for patients with unexpected antibodies for whom there could
be difficulties in finding matched blood for transfusion.
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Ko, et al.
This work was supported by 2005 Inje University research
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